FINGERPRINTS
In the public's mind, the fingerprint holds an almost Sherlock Holmesian mystique as a crime-busting tool. But in reality it should probably have the status of a Paul Drake (Perry Mason's baggy-trousered private eye): useful, yes, but only in some cases.
True, as a means of identification, the fingerprint is almost without equal. But the key is finding and using them. Consider that in burglary and property crimes prints are found in only 30 to 40 percent of the cases. Of these, maybe 10 percent will help police get a positive ID on a suspect - if police have a good idea of who did it to begin with. If not - if they have to rely on prints to discover who a criminal is - the probabilities of success can be less than 1 in 100.
Now, however, several techniques are emerging that may improve the odds. The tools, ranging from chemistry to computers, won't fill jails with criminals. But they should raise the status of the fingerprint as a means of criminal identification.
One is the growing use of a chemical found in quick-bonding glues to form fumes that ''smoke out'' and harden fingerprints quickly. Traditionally, latent prints have been raised by dusting surfaces with powders or applying chemicals that react with the amino acids secreted from fingertips. These methods work fine, but the problem is finding the prints and avoiding damage with the brushing.
Enter the new chemistry. A series of pads, each containing a catalyst, is doused with two cyanoacrylate solutions. Cyanoacrylate is the main ingredient in Super Glue. When brewed in an enclosed area, the solutions create smoke that reacts with and reveals the prints. The pluses: Prints can be found on surfaces normally tough to tackle - money, tape, leather, and plastic bags. The use of cyanoacrylate can also be quicker than dusting. And, by hardening the prints, it leaves a permanent record.
Variations of the technique, discovered by British police through a bit of serendipity a few years ago, are now being marketed by about six United States companies. Dura-Print Technologies of San Francisco, for example, makes kits (from $25 to $400) that can be toted to a crime scene in a briefcase. Some 2,000 police agencies are trying various versions.
Some reasons forcaution exist, however: Chemicals in some products have caused problems with prints that have blood or grease on them, police say. ''It's not a panacea, but what it does is identify latent prints in areas where technicians may not want to spend the time dusting,'' says Robert McCrie, publisher of Security Letter, an industry newsletter.
A sleuthing tool with even greater reach is the computer. It isn't used for lifting but rather for analyzing prints. Normally, detectives take crime-scene prints and manually try to match them with ones on file. It's a time-consuming, hit-or-miss task: A big city agency may have more than a million sets of prints on cards. Even if police already have a suspect in mind, it may take weeks to rifle through the cards and make an ID - and then only if they have good prints to work with. For a ''cold'' search, using crime-scene prints to identify an unkown criminal, the task is taller and the odds infinitely shorter.
Computers speed up the process. Systems are operating that can compare crime-scene prints with those on file at the rate of 650 per second. Computer comparisons also come closer to being foolproof: Like fingerprint experts, the machines analyze the unique architecture of each print by counting and determining the positions and directions of ridges and loops and whorls. But they can also enhance prints by filling out damaged or partial finger signatures.
As a result, machines can make IDs of the most likely suspects from distorted and partial prints - and improve the chances of ''cold hits.'' Houston police used to turn up about one suspect a year from manual cold searches through print files. Now they are ''hitting'' 30 or so a month with an automated system. San Francisco police have been getting close to a 19 percent arrest rate on cold searches since installing a computer in February. ''There is not anything that has come about in the last 50 to 100 years that has had this much impact on solving crimes,'' contends San Francisco Sgt. Kenneth Moses.
Snags exist, though. One is cost - $1 to $2 million for a large system. Computers also require maintenance. And each print card has to be optically scanned for entry into the computer - a task that took six months with San Francisco's 2.5 million prints. Automated systems have been around for several years, but police are only now starting to install them. Less than two dozen agencies now have systems supplied by the two main vendors, NEC Information Systems (Boxboro, Mass.) and De La Rue Printak Inc. (Anaheim, Calif.).
Other fingerprint techniques are gaining, too - including the use of lasers (effective but costly), and new dyes and flourescent compounds. The upshot of all this, says Dr. Henry Lee, head of Connecticut State Police's forensic lab, is that the detective of the future will use many different tools to lift prints. Thus, with science increasingly replacing instinct and intuition, fingerprinting may start to fulfill its inflated image as a crime-buster.
