OVER THE PAST 200 YEARS, VARIOUS MEANS OF IDENTIFYING AND KEEPING RECORDS OF CRIMINALS HAVE BEEN USED, INCLUDING REGISTERS OF HABITUAL CRIMINALS, PHOTOGRAPH ALBUMS OF CONVICTS AND OTHER HABITUAL CRIMINALS, THE FRENCH ANTHROPOMETRIC SYSTEM (CERTAIN MEASUREMENTS OF VARIOUS PARTS OF THE BODY WERE RECORDED FOR EACH PRISONER), AND FINGERPRINT IDENTIFICATION SYSTEMS. CRIME SCENE FINGERPRINTS, FOR THE LATTER, ARE DETECTABLE IN ONE OF THREE WAYS: (1) AS IMPRESSIONS IN A SOFT SUBSTRATE SUCH AS PUTTY; (2) AS LEGIBLE IMPRESSIONS MADE BY FINGERS CONTAMINATED WITH PAINT, BLOOD, OIL, ETC.; AND (3) AS LATENT OR INVISIBLE IMPRESSIONS WHICH ARE IDENTIFIABLE BY EXPLOITATION OF THE NATURE OF THE MARK ITSELF AND THE SUBSTRATE IT IS FOUND ON. FROM THE 1960'S ON, THIS LAST CATEGORY HAS ENGENDERED A LARGE AMOUNT OF RESEARCH. A LATENT IMPRESSION CONSISTS OF 98 TO 99.5 PERCENT WATER AND .5 TO 2 PERCENT SOLIDS IN VARYING FORMS. LATENT IMPRESSIONS ON HARD FIRM SURFACES SUCH AS METAL OR GLASS NORMALLY ARE MADE VISIBLE BY APPLYING A FINGERPRINT POWDER. HOWEVER, ONGOING RESEARCH IS CONCERNED WITH MEANS OF RETRIEVING PRINTS MADE IN MORE DIFFICULT SUBSTRATES USING VACUUM DEPOSITION OF THIN METAL FILMS; USING METALS LIKE LEAD, GOLD, SILVER, CADMIUM, AND ZINC; APPLYING RADIOACTIVE SULPHUR DIOXIDE OR GENTIAN VIOLET; OR EMPLOYING THE PROCESS KNOWN AS 35 SPD. SEVERAL CASE HISTORIES ILLUSTRATE THE IMPORTANCE OF FINGERPRINTS TO CRIMINAL INVESTIGATIONS. (PRG)