Hand-considered hypotheses, 5401–5500
Forensic physical science, written one at a time. The hundred entries below are restricted to physical and chemical mechanisms: what trace material does when it crosses a contact, how materials record their processing and their damage, how projectiles and fractures spend energy, what fire leaves in char and soot, which post-mortem changes are clocks and which are thermometers, and what the instrument itself adds to the number it reports. Each entry carries the logical form chosen for it and no label is repeated, so the variety is structural rather than topical. None has been tested; no data are reported and no citation is made. The single figure offered as a range is flagged in place as an estimate, no measured value appears anywhere in this file, and no entry makes a legal or procedural claim.
Transfer, persistence and the contact
Hidden rate variable
H5401. Treating trace transfer at a contact as a product of load and time misses the variable that actually sets it, which is the number of asperity junctions that form and release, and that number saturates once the two surfaces have conformed. Repeated light contacts at the same total load should therefore deposit more than one sustained press of equal load-time. Counting particles per square millimetre on the receptor after matched load-time integrals, with the surfaces pre-conformed in a control arm, separates the two readings.
Two populations misread as one decay
H5402. Soil persistence on a shoe sole looks like a single exponential when it is the sum of two losses, grains shaken off in the first steps and grains held by moisture bridges that survive until the bridge evaporates. Drying the sole before walking should move material from the slow population into the fast one and bend the curve without changing the total load. Weighing the sole at every step in a humidity-controlled corridor makes the two populations visible as separate slopes.
Non-monotone humidity response
H5403. Fibre transfer onto upholstery should peak at an intermediate relative humidity rather than rising or falling monotonically, because a dry fabric holds charge that attracts fibre ends while a damp fabric dissipates the charge and adds capillary adhesion only at the contact points. Somewhere between roughly thirty and sixty per cent relative humidity, an estimate rather than a measurement, the two effects cross, so an experiment run at ambient humidity may sit on either side of the maximum. Running the same donor-receptor pair across a humidity series, with charge measured on the receptor, places the peak.
Saturation bound
H5404. Secondary transfer of glass from one receptor to another is limited by the first receptor's own loading, because the number of retention sites on its surface is finite, so additional primary fragments stop increasing what it can pass on. Delivering a graded series of primary loadings to identical shoes and stepping each onto a clean surface gives the plateau where the secondary count flattens while the primary count keeps rising.
Geometric signature
H5405. Gunshot residue on a shooter's hands is often read as symmetric, but the ejector port and the grip together produce a directional lobe whose axis is fixed in the firearm's frame. Rotating the grip through a series of angles should rotate the lobe with the port rather than with the hand. Sampling a grid across the thumb web and plotting particle density against the port's angle separates the firearm's geometry from the shooter's.
Discrete modes instead of a continuum
H5406. Residue particles from a given primer should not be continuously distributed in size, because two formation routes, condensation from vapour and agglomeration of condensate, produce two modes separated by a gap. The gap sits where the agglomeration's collision time exceeds the plume's cooling time, so it should shift with the plume's dilution. Sampling at several distances in a closed test chamber and plotting size distributions shows whether the gap moves outward.
Sampling tool as source
H5407. Adhesive lifts carry their own particle burden, because particles trapped in the adhesive during manufacture are mobilised when the tape is warmed or flexed. The contribution scales with the tape's age and storage temperature rather than with the surface being sampled. Running a blank lift from a cleaned, dust-free plate for every batch of tape gives the per-lift background that a sample must exceed.
Sign reversal from a compliance ratio
H5408. Smear taper on a transferred paint flake is read as a direction indicator, but the taper should reverse when the painted substrate is more compliant than the tool, because the transfer becomes a peel rather than a scrape. In a peel the softest layer is left behind last, so the feather points opposite to the motion. Painting rigid panels and elastomer panels with the same coating and dragging an identical tool across both separates the two cases.
Misattribution to the residue
H5409. Contrast of a latent print on polished metal is credited to the residue's absorbance, but most of the visible print is likely the oxide layer's thickness change under the residue's salts. A print on a sputtered oxide film of known thickness should then show contrast that scales with film thickness at constant residue. Comparing prints on the same metal with and without the oxide layer, imaged at the same illumination, separates the contributions.
Shear-direction record
H5410. Shedding from skin at a contact should depend on the shear direction as well as the pressure, because flakes detach when the interface's shear exceeds their intercellular adhesion and the detachment front propagates down-shear. A contact made with a twisting motion should deposit an asymmetric patch whose long axis follows the twist. Depositing on glass with controlled normal load and twist angle, then counting flakes per field, tests whether the asymmetry is a direction record.
State-dependent measurand
H5411. Impression depth in soil is read as a proxy for body mass, yet depth is set mainly by the soil's antecedent state, its pre-existing compaction and water content, so two people of equal mass can leave depths that differ by more than the range across masses. The mechanism is that bearing capacity depends on suction, which is lost as the soil is disturbed. Footprints made on a prepared bed at several controlled water contents, with known loads, give the depth-mass relation as a family of curves rather than one line.
Measurement medium alters the measurand
H5412. Colour measured on a soil in air is darker and redder than the same soil measured under water, because the adsorbed film changes the effective refractive index at the grain surfaces. Comparisons made under different ambient humidities therefore carry a colour difference that belongs to the laboratory. Spectrophotometry of one sample in a controlled chamber, ramping humidity while holding temperature, separates the film's contribution from the soil's mineralogy.
Geometric similarity argument
H5413. Deposit profiles along a vehicle's underbody should collapse onto one curve when plotted against the length of the recirculation zone behind the front axle, rather than against distance from the bumper. Two vehicles of different size driven at different speeds should then show the same profile in that length scale. Measuring the recirculation length by tuft or smoke visualisation and rescaling the deposit profile tests whether one geometric variable organises the data.
Inversion of an expected monotonicity
H5414. Pick-up of fibres on a blade should rise with penetration depth only until the fabric's elastic recovery begins to wipe the blade on withdrawal, beyond which the blade can leave with fewer fibres than it carried in. The signature is a maximum in pick-up at a depth comparable to the fabric's thickness. Stabbing a layered fabric stack at graded depths and counting fibres on the blade, with the stack's thickness varied independently, tests the inversion.
Donning motion recorded in a deposit
H5415. Powder shed from a glove should map the glove's donning motion, because the hand's passage displaces the powder film toward the cuff. A surface touched before donning should then carry more powder at the fingertips, and one touched after donning more from the palm. Sampling a glove's exterior in zones before and after donning, and transferring each zone to a clean plate, tests the mapping.
Material property hidden as a case variable
H5416. Retention of crystalline explosive particles on a polymer should track the difference in surface energy between particle and polymer rather than the particle's size, because adhesion is dominated by van der Waals contact once the particle is smaller than the surface's asperities, so two polymers of equal roughness but different surface energy should retain very different amounts. Pressing a standard particle bed onto a series of polymers of graded surface energy, and counting retained particles, isolates the term.
Coincidence bound on apparent uniqueness
H5417. Torn tape ends are matched by the striations left at the tear, but those striations are produced by the backing's weave, so two tears can share a pattern without sharing an origin. The crack follows the weave's float boundaries, and the float pattern repeats along the roll. Tearing one roll at many points and comparing striation patterns pairwise tests how often a coincidental match arises.
Variance partition
H5418. Between-donor variance in trace transfer should exceed within-donor variance for the same material, because each donor's surface roughness and moisture set transfer efficiency more than the contact does. If this holds, per-contact transfer probabilities pooled across donors misstate any single contact by a wide margin. A crossed design with several donors, repeated contacts and two materials partitions the variance directly.
Overlap with a hidden discriminator
H5419. Brake-wear spherules and fly-ash spherules overlap in major-element composition but should differ in the crystallinity of their outer shells, because brake wear forms by oxidation of a molten droplet in air while fly ash forms inside a coal particle's reducing interior. Shell crystallinity measured by electron backscatter diffraction should then separate them where composition cannot. Collecting both populations from a single roadside dust sample and indexing the shells tests the discriminator without assuming a source.
Ring as a size record
H5420. Aerosolised paint droplets from a spray can should carry a solvent-rich core, so a droplet that lands and dries leaves a ring whose diameter records the droplet's original size rather than the spray's cone angle. The ring forms because solvent evaporates fastest at the pinned edge and drives an outward flow that carries pigment there. Measuring ring diameters on a surface at graded distances from the nozzle tests whether the ring is a size record.
Fibres, hair, textiles and coatings
Depth-resolved discriminator
H5421. Fading of a dyed fabric under light should be confined to a layer thinner than the fibre's radius, because photodegradation of the dye is limited by oxygen diffusing into the fibre. A colour difference between two pieces of the same fabric may therefore record the reference's light exposure rather than a different dye lot. Sectioning a fibre and mapping fluorescence across its diameter distinguishes surface fading from the through-thickness change produced by washing.
Processing history recorded in geometry
H5422. Twist-reversal spacing in cotton should record the tension at which the fibre dried, because a reversal forms where the collapsing lumen buckles under drying stress. Two fabrics woven from the same yarn count can then differ in spacing without differing in variety. Measuring spacing along many fibres from each fabric, with drying tension varied in a control batch, tests the record.
Observation-condition artefact
H5423. Medulla visibility in hair is often an optical result rather than an anatomical one, because the medulla's air-filled spaces can be index-matched by the mounting medium at the cut's angle, so reported frequencies of medullated hairs depend partly on the mountant. Imaging one hair dry, in air and in two media of different index should make the medulla appear and disappear without the hair changing.
Ambient term in a material constant
H5424. Birefringence of a regenerated cellulose fibre should change with the fibre's moisture content, because water disrupts the amorphous orientation that contributes to the measured retardation. A fibre measured in a dry room and the same fibre equilibrated at high humidity should differ by more than the between-fibre spread. Running a compensator measurement inside a humidity-controlled stage over a ramp separates the moisture term from the orientation term.
Substrate-dependent morphology
H5425. Bead shape at a melted fibre's end should depend on the substrate it cooled on, because the bead's contact angle with that substrate decides whether it freezes spherical or flattened. Two identical garments melted against different surfaces should therefore yield beads of different shape, and shape should not be read as a fibre property. Melting single fibres on a graded series of substrates of known surface energy and measuring bead height against width tests the dependence.
Misattributed cause of a pattern
H5426. Crack networks in automotive clearcoat should follow the primer's thermal expansion mismatch with the substrate rather than the clearcoat's age, because crack spacing is set by the strain energy released at the primer's thickness. A repainted panel and an original panel of the same age should then differ in crack density. Thermally cycling panels with and without a primer, at matched clearcoat thickness, separates the two.
Order inversion during transfer
H5427. A smeared paint transfer can present its layers in reverse order, because the softer layer smears furthest and ends up on top of the harder one. Reading layer sequence from a smear as if it were a cross-section therefore inverts part of the stratigraphy. Dragging a known multilayer chip across glass at graded loads and imaging the smear by confocal microscopy shows the inversion directly.
Transient that looks like a spectrum
H5428. Pigment Raman spectra should drift during the first seconds of illumination and then stabilise, because the laser bleaches a thin surface layer until the probed volume lies behind the bleached zone. Spectra collected with different exposure times are then not comparable, and the difference can look like a pigment difference. Collecting a time series at fixed power on one spot, and repeating at a second spot, places the plateau and shows whether it belongs to the pigment or the operator.
Conditional coincidence
H5429. Metameric pairs should be more common among dyed blacks than among saturated colours, because a black is built from several absorbing dyes whose combined spectra can be matched in more than one way. Two blacks that match under daylight can then diverge under tungsten, and the divergence is a property of the dye mixture as much as of the illumination. Measuring reflectance under a daylight simulator and under tungsten for a set of blacks, and counting pairs whose difference changes sign, tests the claim.
Ambiguity between two mechanisms
H5430. Cut and torn fibre ends are harder to separate than the usual distinction implies, because a fast tear suppresses the fibrillar pull-out that a slow tear leaves and produces a flat, granular end. The appearance then depends on the rate at which the fabric failed rather than on the tool. Pulling single fibres at controlled rates across several decades and imaging the ends tests whether morphology maps rate rather than mechanism.
State at the moment of contact
H5431. Scale impressions pressed into a soft surface should depend on the hair's hydration at the moment of contact, because cuticle scales are softest when swollen, so two contacts of the same head of hair at different humidities should give different impression depths. Pressing one hair into a polymer at controlled humidities and profiling the impressions tests whether depth records the environment.
Age proxy confounded
H5432. Crystallinity of a polyethylene bag should fall as the bag absorbs solvent, because the solvent lowers the polymer's melting point and lets crystalline regions reorganise at ambient temperature. An apparent age difference read from crystallinity can then be an exposure difference. Annealing pieces of the same bag at a series of temperatures and measuring crystallinity after each gives the mapping that solvent exposure would otherwise imitate.
Two clocks at different rates
H5433. Fluorescence of an adhesive residue should decay with light exposure faster than its colour changes, because the adhesive's photoinitiator fragments quench the fluorophore before the bulk yellows. An age read from fluorescence is then an exposure record. Exposing residues on glass to a controlled lamp for graded times and measuring both fluorescence and colour gives two clocks that run at different rates.
Count bound on apparent randomness
H5434. Yarn-end configurations in a torn fabric are bounded by the weave's float length, because the tear must follow either a warp or a weft float at each step, so the apparent randomness of a torn edge is a constrained walk and the count of plausible matches is smaller than an unconstrained estimate would suggest. Tearing several specimens from one cloth and counting distinguishable edge configurations tests the bound.
Additive artefact
H5435. Microspectrophotometric colour of a fibre should include the mounting medium's fluorescence when the instrument's source is rich in ultraviolet, because the medium emits into the same collection path as the fibre. Two laboratories using different media can then report different colours for identical fibre. Measuring one fibre in three media and subtracting each medium's blank separates the offset from the fibre's own spectrum.
Glass, ceramics, soils and minerals
Thermal overwriting
H5436. Refractive index of a glass fragment should shift when the fragment is annealed well below softening, because the fictive temperature set during manufacture is partly erased. A fragment recovered from a fire can then match a different source's glass better than its own. Re-annealing fragments of known source at graded temperatures and re-measuring index gives the shift and shows whether it exceeds the between-source spread.
Hidden time axis in a spacing
H5437. Wallner lines on a fracture surface should be spaced in proportion to the crack's velocity history rather than to the stress intensity alone, because each line marks the crack front's interaction with an acoustic wave the crack itself launched. The spacing then encodes the impact's duration. Breaking glass with a controlled impactor at graded pulse durations and measuring line spacing on the fracture surface tests the encoding.
Time-dependent count
H5438. Fragment count from tempered glass should keep rising after the break, because stored strain energy continues to drive branching for a short interval. A count made immediately and a count made after handling will therefore differ, and the difference belongs to the measurement's delay rather than to the glass. High-speed imaging of the fragmentation, with counts extracted frame by frame, gives the count's time dependence.
Protocol-induced difference
H5439. Oven drying changes the particle-size distribution of a soil, because drying aggregates clay platelets and the aggregates survive the sonication energy usually applied. Two soils from different sites can then appear more similar after standard preparation than they are in place. Measuring one sample at graded sonication energies and comparing the plateaus separates aggregate strength from a genuine site difference.
Anisotropy as discriminator
H5440. V-shaped impact pits on quartz grains should align with crystallography rather than randomly, because the pit walls follow the easiest cleavage planes and the impact's direction only selects which planes are exposed. The orientation distribution then carries a signature of the transport that randomises grain rotation. Imaging pits by confocal microscopy and indexing their walls to the grain's axes tests whether orientation clusters by site.
Transformation marker
H5441. Reddening of soil at a fire scene should be read as a transformation rather than a source difference, because goethite dehydrates to hematite at temperatures reached in the top centimetres of a soil. A reddened patch therefore records the fire's thermal footprint and not a different soil. Heating splits of one soil at graded temperatures, then measuring colour and magnetic susceptibility, gives the transformation curve.
Specimen preparation selects the answer
H5442. Peak-intensity ratios in a clay's X-ray pattern should depend on how the specimen was prepared, because settling or pressing aligns the platelets and alignment raises some reflections at the expense of others. A mineral ratio computed from those intensities can then be a preparation artefact rather than a composition. Preparing one clay by drop-drying, smear and side-loading, and comparing the three patterns, shows the range that preparation alone can produce.
Narrow population as a discriminator
H5443. Road-marking beads should be distinguishable from container glass by their narrower index distribution, because the beads are drawn from a batch selected for retroreflectivity, and their surfaces should also carry an alkali-depletion layer formed during flame spheroidisation. Measuring index distributions and surface alkali by XPS for both populations tests whether the two criteria agree.
Gradient orientation
H5444. Vitrification gradients across a sherd should record which face saw the kiln, because the face nearer the flame reaches a higher temperature and develops more glassy phase. A sherd's orientation during firing can then be read from a polished cross-section. Firing replicate briquettes with one face shielded and one exposed, and mapping the glassy phase across the thickness, gives the gradient's direction.
Projection bias
H5445. Roundness measured from a two-dimensional image should underestimate the three-dimensional value systematically, because a projected outline reports the grain's largest silhouette rather than its mean section, so comparisons between sites can be biased by the grains' preferred orientation on the slide. Measuring the same grains by X-ray tomography and by image analysis, and comparing the two distributions, quantifies the projection bias.
Correlation that does not transport
H5446. Density and refractive index correlate within a glass family because both follow the alkali-to-silica ratio, but the slope should differ between families using different alkaline earths. Two glasses from different plants can then share an index and still differ in density. Collecting fragments of known plant origin and plotting density against index for each plant separately tests whether the relation transports.
Fabrication direction recorded
H5447. Alkali-silica cracks should orient with a concrete element's casting direction rather than randomly, because the gel expands against the aggregate's restraint and the restraint follows the casting's aggregate alignment. The crack pattern then records fabrication rather than environment. Casting prisms with and without vibration, and mapping crack orientation after accelerated expansion, tests the alignment.
One observable, two causes
H5448. Cone angle of a hole in a glass pane should depend on the projectile's velocity as well as its mass, because the angle is set by how far the pane deflects before it fails and the deflection grows with the impact's duration. Two impacts of equal momentum can then give different cone angles. Firing spheres of graded mass at graded speeds and measuring cone half-angles on recovered panes separates the two dependences.
Internal, external and terminal ballistics
Duration versus peak
H5449. Firing-pin drag on a primer should depend on how long the pressure stays high rather than on its peak, because the primer cup flows around the pin only while the pressure exceeds the cup's yield stress. Two loads of equal peak pressure but different duration should then leave different drag marks. Firing a series with graded propellant burning rates at matched peak pressure, read from a pressure transducer, tests the duration dependence.
Elastic correction
H5450. Case-head expansion after firing should underestimate the chamber's diameter by the elastic recovery of the brass, and the recovery differs between alloys, so two cartridges fired in one chamber can report different chamber sizes. The case springs back while the chamber does not. Firing matched cartridges of different brass hardness through one barrel, and measuring heads before and after, gives the alloy's contribution.
Optimum with opposing terms
H5451. Bullet yaw at short range should reach a minimum at an intermediate twist rate rather than falling monotonically as twist tightens, because a faster twist amplifies any initial yaw while a slower twist lets the overturning moment grow before the yaw can damp. The minimum should sit at a twist set by the bullet's length and its muzzle velocity. Firing one bullet from barrels of graded twist and measuring yaw at a fixed near distance, by shadowgraph or paper, places the minimum.
Nuisance variable in a fitted coefficient
H5452. Ballistic coefficients fitted from velocity decay should absorb the wind's vertical component, because a vertical headwind changes the drag the bullet experiences while a horizontal crosswind does not. Fits made on days with different shear then differ without any change in the bullet. Measuring velocity at several stations with anemometers along the path, and refitting with the measured components, tests the absorption.
Reattribution of a deflection
H5453. Deflection of a bullet after glass should be mostly the yaw the glass induced rather than a lateral push from the glass, because a yawed bullet's centre of pressure sits off-axis and the resulting side force grows with yaw. The deflection should then reverse when the induced yaw reverses. Firing through glass at graded angles and imaging yaw immediately behind the pane separates the two contributions.
Saturation of a deformation
H5454. Final diameter of an expanded bullet should be bounded by the jacket's mouth thickness rather than by impact velocity above the velocity at which the petals fold back, because the petals can open only as far as the mouth allows, so a velocity series should show diameter rising and then plateauing. Recovering bullets fired into a recoverable medium at graded velocities, and measuring each mouth thickness, tests the bound.
Plateau after a regime change
H5455. Penetration of a non-deforming bullet in gel should rise with impact energy at fixed presented area, but a bullet that upsets on impact should show depth independent of velocity above the upsetting threshold. The transition should coincide with the onset of visible deformation. Firing a graded velocity series and measuring both depth and recovered diameter locates the transition.
Medium measured by its own response
H5456. Pulsation frequency of the temporary cavity should measure the gel rather than the bullet, because the frequency is set by the gel's bulk modulus and the cavity's radius and only weakly by the projectile. Two gels poured at different concentrations should then show different frequencies for identical shots. Recording cavity wall motion by high-speed video for gels of graded concentration tests the relation and calibrates the medium.
Distance signature of a mixture
H5457. Droplet sizes in backspatter should be bimodal, because a coarse mode comes from capillary breakup of a liquid ligament and a fine mode from the burst of a bubble trapped in the wound. The two modes should respond differently to distance, since the fine mode travels with the gas flow and the coarse mode with momentum. Collecting droplets on targets at graded distances and measuring size distributions separates them.
Angular signature of a device
H5458. Muzzle devices should leave an angular signature in the residue plume, because ports vent gas sideways and dilute the plume before it leaves the muzzle. The particle density against angle should then be wider for a compensated barrel than for a plain one. Firing matched ammunition through barrels differing only in muzzle device, and sampling on a cylindrical array, tests the signature.
Direction reversal from hardness
H5459. Striations on a soft workpiece should sometimes be the harder tool's own surface features transferred in positive relief, because the harder body indents the softer one along the sliding direction. The mark's asymmetry then reverses compared with the usual negative reading. Sliding hardened and softened tools of identical shape across lead and brass at matched loads, and imaging striation cross-sections, tests the reversal.
Transient with a decay constant
H5460. First-shot shift from a cleaned barrel should decay over a few shots, because residual oil in the bore alters the bullet's friction and the film is consumed shot by shot. The convergence should be a decay whose constant is set by the oil's viscosity. Firing groups after cleaning with oils of different viscosity, and recording first-shot offset against shot number, tests the decay.
Boundary crossing in flight
H5461. Bullets stable at supersonic speed can lose stability as they slow through the transonic region, because the centre of pressure moves as the shock structure changes and the stability margin can pass through zero. The bullet then yaws before recovering or tumbling. Firing long range and measuring yaw at many distances, or tracking with Doppler radar, would show the yaw maximum near the transonic speed.
Material property modulating a geometric one
H5462. Shotgun pellet spread should depend on the shot's hardness as much as on the choke, because soft pellets deform at setback and deformed pellets diverge. Loads of the same nominal size and velocity but different antimony content should pattern differently through one choke. Patterning both at graded distances and recovering pellets to measure deformation separates the material term.
Proxy measurement
H5463. Rifling engraving width on a fired bullet should be a hardness measurement, because width is set by how far the lands penetrate before the bearing surface yields. A softer bullet should engrave wider at the same chamber pressure. Firing bullets from a graded alloy series through one barrel and measuring engraving width and depth tests the proxy.
Timing not force
H5464. Where a case lands after ejection should be set by the extractor's release timing rather than by the ejector's force, because the case leaves the port at the position the slide has reached when the ejector strikes. The landing zone should then shift with the recoil spring's rate rather than with the ejector's shape. Recording landing positions for identical ammunition with graded recoil springs tests the timing dependence.
Two regimes in one power law
H5465. Terminal fragmentation of a bullet should follow a power law in impact velocity whose exponent changes at the velocity where the jacket's strain rate passes its ductile-to-brittle transition. Below that velocity the jacket peels, and above it the jacket shatters. Recovering fragments from gel across a graded velocity series and plotting fragment count against velocity on logarithmic axes locates the change in exponent.
Non-monotone calibration
H5466. Ricochet marks should not lengthen monotonically with approach angle, because a very shallow impact skips and leaves a short mark while a steeper one ploughs and leaves a long one. Mark length itself therefore has a minimum at an intermediate angle. Firing at a steel plate at graded angles and measuring mark dimensions by profilometer tests the non-monotonicity.
Fire debris and combustion
Differential partitioning
H5467. Recovery of an ignitable liquid from wet debris should fall sharply, because water fills the pores and the liquid's lighter compounds partition into the water rather than into the headspace. A negative result can then record the extinguishment rather than the absence of accelerant. Extracting replicate debris samples at graded water contents and quantifying recovery against an added standard gives the suppression curve.
Two processes with one signature
H5468. Normal-alkane envelopes used to read an accelerant's evaporation should be distorted by the substrate's preferential adsorption of aromatics, because aromatic molecules interact more strongly with polar sites on char and clay. A pattern that looks like heavy evaporation can then be a substrate effect. Spotting one liquid onto several substrates and comparing the envelope after equal evaporation times separates the two.
Material property as a thermometer
H5469. Char conductivity should map the maximum temperature it reached, because pyrolysis progressively graphitises the residue and conductivity rises with the extent of graphitisation. A charred timber's cross-section should then carry a conductivity profile readable as a temperature profile. Measuring conductivity along a charred section with a four-point probe, against thermocouples embedded during a replicate burn, tests the mapping.
Mode recorded in morphology
H5470. Soot from smouldering should be larger and more compact than soot from flaming combustion, because smouldering produces particles at lower temperature with longer residence and more coagulation before oxidation. That contrast should then be readable by electron microscopy alone. Collecting soot on grids from controlled smouldering and flaming burns of one fuel tests the morphology difference.
Hidden state variable
H5471. Spalling depth in concrete should depend on the moisture at the exposed face more than on the fire's temperature, because spalling is driven by vapour pressure built up behind a drying front. Two faces of one element with different curing histories should then spall to different depths in the same fire. Casting panels at graded moisture contents and exposing them to a replicate heat flux, with depth measured by ultrasonic transit time, tests the dependence.
Distinct feature, same angle
H5472. Thermal and mechanical cracks in glass should differ in the regularity of branching rather than in branching angle, because thermal cracking advances under a steadily rising stress field while mechanical cracking advances under a decaying one. Thermal cracks should then branch at more even intervals. Comparing branch spacing from panes exposed to a radiant panel and panes broken by impact tests the discriminator.
Alternate cause for a pattern
H5473. Burn patterns on a floor should sometimes be the joint layout controlling airflow rather than the liquid's spread, because the liquid burns where vapour mixes with air and the joints feed air into the boundary layer. A poured line crossing a joint-free panel should then burn differently from one along a joint. Pouring identical quantities across jointed and joint-free panels and mapping burn depth tests the alternative cause.
Container as a competitor
H5474. Headspace recovery from a debris can should depend on the can's own adsorption sites, because the lining and the crimp take up a fraction of the vapour and that fraction changes with the can's history. A new can and a re-used can should then give different recoveries from identical debris. Adding a known mass of liquid to clean cans of several histories and measuring headspace by gas chromatography gives the can's uptake.
Break in a constant rate
H5475. Charring rate in timber should not be constant with time; it should step upward when shrinkage cracks in the char open a path for pyrolysis gases, because the cracks reduce the layer's insulating value. The step should appear at a char depth set by the wood's shrinkage. Burning instrumented timber samples and measuring char depth continuously rather than at the end tests the step.
Material-dependent geometric signature
H5476. Apex angles of V patterns on walls should depend on the wall's thermal effusivity as well as on the flame's standoff, because soot deposition requires the surface to stay below a threshold temperature and effusivity sets how fast that threshold is reached. Two walls of different material should then show different apex angles for the same fire. Burning a controlled fire against walls of graded effusivity and measuring the pattern's angle tests the dependence.
Dominance question
H5477. Pool radius from a melted polymer should be more sensitive to floor slope than to the polymer's melt flow index, because gravity-driven spreading dominates capillary spreading at the pool sizes typical of a fire. The pool's final shape should then record the floor's tilt. Melting identical charges on floors at graded tilts with graded melt flow indices tests which variable dominates.
Inversion of a sequence
H5478. Aromatic fractions in porous substrates should persist longer than alkanes, inverting the usual weathering order, because aromatics adsorb more strongly to polar sites and are therefore less available to evaporate. A residue that looks heavily weathered by its alkane loss can then be comparatively fresh. Weathered residues in several substrates, quantified against a deuterated standard, test the inversion.
Inversion problem with a unique solution
H5479. Thickness profiles of soot on a cold surface should follow boundary-layer growth along that surface, so the profile can be inverted to give the smoke's duration and the surface's temperature. The inversion should be unique because deposition velocity is monotone in surface temperature. Depositing soot on cooled plates at graded temperatures in a controlled smoke stream and comparing profile shapes tests the inversion.
Stoichiometric record in soot
H5480. Nitrogen retained in soot should record the fuel's nitrogen and the combustion temperature, because fuel nitrogen is released as hydrogen cyanide at high temperature and retained in the soot at low temperature. The soot's nitrogen content should therefore be a temperature record. Burning nitrogen-bearing and nitrogen-free fuels at graded temperatures and measuring soot nitrogen by XPS tests the record.
Post-mortem physical and chemical change
Boundary condition assigned to the wrong surface
H5481. Early post-mortem cooling should be dominated by conduction into the supporting surface rather than by convection to the air, because the contact's thermal resistance is much lower than the air's. The early slope should then change with the surface material and be steeper on tile than on carpet. Cooling body analogues on surfaces of graded conductivity, with core and surface thermocouples, tests the boundary assignment.
Parameter that is not constant
H5482. Shape factors used to summarise a body's cooling should not be constant through the cooling, because the factor depends on the ratio of surface area to volume and the effective surface changes when the core-to-surface gradient reverses. The factor should shift at the reversal, producing a kink a single exponential cannot fit. Cooling a body analogue with an array of thermocouples and fitting the curve in segments locates the kink.
Wrong rate-limiting step
H5483. Potassium's rise in the vitreous should be limited by release from the lens and ciliary body rather than by diffusion through the vitreous, because the diffusive time across the vitreous is shorter than the observed rise. The rise should then be insensitive to the vitreous's volume. Measuring potassium at several sites within one eye, and in eyes of different volumes, tests which step limits the rise.
Temperature-scaled clock
H5484. Fixation of lividity should be a gelation of blood in the dependent vessels rather than a settling of cells, because the fixation front advances in a way that settling alone cannot produce. Fixation should then be slower at low ambient temperature, following the gelation's temperature dependence. Grading fixation in bodies held at different ambient temperatures, or in a controlled animal model, tests the temperature scaling.
Clock reading another variable
H5485. Rigor onset should depend more on muscle glycogen at death than on ambient temperature, because the time to ATP depletion is set by stored glycogen and glycolytic rate together, so two bodies at one temperature can differ widely. Sampling muscle glycogen at death in an animal model and timing rigor onset in matched limbs tests the dependence.
Self-heating plateau
H5486. Bodies decomposing in sealed containers should hold a temperature plateau above ambient, because the exothermic decomposition's heat is retained by the container's insulation while the same body in open air loses it. The plateau's height should then be a property of the container as much as of the body. Decomposing matched analogues in containers of graded insulation, with internal thermocouples, tests the plateau's origin.
Layered recorder
H5487. Adipocere should form in layers that record fluctuations in the immersion water's chemistry, because each layer's composition is set by the calcium and pH at the time it formed. A cross-section should then be readable as a sequence rather than as a single age. Forming adipocere on matched tissue in water at controlled pH and calcium, changed at known intervals, tests whether the layers preserve the sequence.
Environment-confounded clock
H5488. Corneal opacity should be a drying front, so its rate should depend on ambient humidity and airflow over the eye rather than on the interval alone. Two eyes in one room under different airflow should then differ. Measuring opacity with a small optical probe on eyes exposed to controlled humidity and airflow tests the dependence.
Two clocks out of step
H5489. Heat in soil beneath a body should dissipate long before the chemical disturbance does, because heat diffuses while the products of decomposition persist and continue to alter the soil's chemistry. A soil's temperature can then be normal while its chemistry is still anomalous, and a thermal estimate of the interval would be far too short. Measuring temperature and pore-water chemistry in one soil column after removal of a heat source tests the difference in recovery.
Directional marker
H5490. Marbling after death should follow the venous tree's flow direction rather than spreading uniformly, because the sulphide that produces the pattern is carried by blood and reacts where it meets the vessel wall, so the pattern's branches should be directional and their orientation should differ between dependent and non-dependent regions. Mapping the pattern against vessel anatomy in an animal model with controlled position tests the directionality.
Clock with a second input
H5491. Bone mineral crystallites should coarsen after death by Ostwald ripening at ambient temperature, so crystallite size should increase with the interval. The rate should depend on the burial's moisture, because ripening needs a water film between crystallites. Measuring crystallite size by X-ray diffraction on buried bone of known intervals across several moisture regimes tests the clock and its second input.
Orientation dependence
H5492. Cooling in water should be faster with a body's long axis vertical than horizontal, because the convective boundary layer is thinner at the leading face and the plume rises along the body. The difference should be large enough to matter over the first hours. Immersing body analogues in a tank at both orientations, with thermocouple arrays, tests the orientation dependence.
Instrumental methods and their preparations
Attenuation by the preparation
H5493. Carbon coating applied for charge control should attenuate low-energy X-ray lines more than high-energy ones, because attenuation scales steeply with wavelength and the coating's thickness varies with the coater's geometry. Two laboratories coating the same particles to different thicknesses can then report different compositions. Measuring one particle at several coating thicknesses, with thickness read from a quartz monitor, tests the attenuation.
Instrument-generated compound
H5494. Compounds that appear only through an aged gas-chromatography inlet liner should be products of the liner, because the deactivated glass's active sites catalyse rearrangements at the inlet's temperature, so such a peak should appear in blanks and disappear with a new liner. Running one extract through liners of graded deactivation, with blanks between, tests the catalytic origin.
Matrix effect with a thermal cause
H5495. Plasma temperature in laser-induced breakdown should depend on the sample's thermal conductivity, because a conductive sample quenches the plasma's early expansion and shifts the temperature at which emission lines form. The matrix effect in calibration should then be predictable from conductivity. Measuring plasma temperature by line ratios on samples of graded conductivity and comparing calibration slopes tests the thermal cause.
Non-monotone roughness response
H5496. Low-energy X-ray intensity from a pressed powder should vary non-monotonically with surface roughness, because roughness both shadows the detector and lengthens the effective path, and the two effects oppose. Light-element quantification should then depend on pressing pressure. Pressing one powder at graded pressures, and measuring roughness by profilometry alongside intensity, tests the non-monotonicity.
Contact-pressure term
H5497. Effective penetration depth in attenuated total reflectance should depend on contact pressure, because the sample's contact with the crystal changes the evanescent field's coupling, and this effect should be larger than the orientation effect usually blamed for spectral differences. Two spectra of one polymer at different clamp pressures should then differ in band ratios. Measuring a single sample at graded pressures, with pressure read from the clamp, tests the magnitude.
Polarization-dependent intensity
H5498. Raman band intensity from an oriented fibre should depend on the laser's polarization relative to the fibre axis, because the band's Raman tensor is anisotropic and drawing aligns the chains. Two fibres of identical chemistry but different draw ratio should then give different band ratios at fixed polarization. Rotating a fibre under a polarized probe, and repeating for fibres of graded draw ratio, tests the assignment.
Fractionation from incomplete conversion
H5499. Isotope ratios from an elemental analyser should be biased when combustion is incomplete, because the uncombusted fraction is isotopically heavier and the measured gas is therefore lighter than the sample. Samples with different matrices can then differ without differing in source. Burning a standard at graded combustion efficiencies, achieved by varying the oxygen dose, tests the fractionation.
Correction parameter as a variable
H5500. Beam-hardening corrections differ between micro-CT scanners, so the same object's density should vary between machines because each reconstruction sets the correction as a free parameter rather than measuring it, and comparisons across scanners therefore carry an arbitrary offset. Scanning a phantom with known inserts on both machines, and re-reconstructing each dataset with one correction, tests the offset.
Status
100 entries, H5401–H5500. Every entry states a claim, a mechanism that would produce it, and a measurement that would separate it from the alternatives. The forms are deliberately uneven in weight: some are bounds, some are inversions, some are artefacts that mimic a real effect, and several are worth writing down only because they can be falsified cheaply.
If one of these is worth an experiment, it is H5467 — that water in fire debris suppresses recovery of the lighter fraction by partitioning into the water rather than the headspace, so a negative result can record the extinguishing water rather than the absence of accelerant. It is checkable with two cans, one wet and one dry, and a standard addition.
Incoprea Research · hand-considered hypotheses 5401–5500 · 3 November 2026 · ~/Desktop/Nov3/