EXPERIMENTAL PROCEDURES WERE DEVELOPED TO DETERMINE THE FOLLOWING: (1) IF FLAKES OF PARTIALLY BURNED SMOKELESS POWDER ARE FOUND ON THE HAND OF A PERSON WHO HAS FIRED A GUN AND IF THEY RETAIN THEIR ORIGINAL VOLATILIZABLE ORGANIC CONSTITUENTS (VOC); (2) IF FILM OR DUST OF VOC IS DEPOSITED ON THE HAND; (3) IF FLAKES ARE CONTAMINATED BY VOC FROM PREVIOUS FIRINGS; (4) THE EFFICIENCY OF THE ACETONE SWAB VOC COLLECTION TECHNIQUE; (5) IF CHARACTERISTIC ANALYZABLE DERIVATIVES ARE FORMED DURING FIRING; AND (6) IF VOC ARE RETAINED ON THE HAND FOR ANY SIGNIFICANT PERIOD AFTER THE FIRING OF A GUN. HAND SAMPLES TAKEN BY ACETONE-SOAKED COTTON SWABS OR TAPE LIFTS WERE ANALYZED DIRECTLY; NO EFFORT WAS MADE TO SEPARATE VOC FROM SKIN OILS OR OTHER POSSIBLE CONTAMINANTS. WHEN THE SAMPLES WERE COLLECTED PROMPTLY, FLAKES OF PARTIALLY BURNED SMOKELESS POWDER WERE FOUND. THE FLAKES WERE SOMETIMES CONTAMINATED WITH VOC, EITHER FROM PREVIOUS FIRINGS OR FROM UNKNOWN SOURCES. THE ACETONE SWAB TECHNIQUE, AT LEAST FOR THE COLLECTION OF DIPHENYLAMINE FROM THE HAND, RESULTED IN A VERY LOW RECOVERY EFFICIENCY WHEN SMALL AMOUNTS OF DIPHENYLAMINE WERE PRESENT. NO CHARACTERISTIC DERIVATIVES WERE DETECTED ON HANDS THAT HAD RECENTLY FIRED A GUN. NO VOC, EXCEPT FOR FLAKES OF SMOKELESS POWDER, WERE DETECTED ON HANDS IMMEDIATELY AFTER HAVING FIRED A GUN. EXTREME CAUTION IS RECOMMENDED WHEN DESIGNATING THAT A POWDER PARTICLE HAS COME FROM A SPECIFIC BRAND AND TYPE OF CARTRIDGE BASED ON GAS CHROMATOGRAPHY-MASS SPECTROMETRY ANALYSIS BECAUSE OF POSSIBLE CROSS-CONTAMINATION FROM PREVIOUS FIRINGS OF DIFFERENT TYPES OF CARTRIDGES. SUPPORTING DATA AND REFERENCES ARE INCLUDED. (DEP)