Scene of the Crime (13 page)

I will add that of all the criminals who, after conviction, have ever promised to "git" me, Leon McCoy is about the only one I think is crazy enough to try. But it was still an interesting case. If you want to read more about it, it's
Leon McCoy
v.
The State of Georgia.
My name then was Martha G. Webb. (Never mind how I turned into Anne Wingate. That's another story entirely.)

Finding Latents en Paper

In general, paper is fumed or sprayed. But highly glazed paper, such as that found in high-quality magazines, is best treated by powders. In one case, the home of an FBI agent was burglarized. On the back of the FBI magazine found on the agent's nightstand was an enlarged photograph of an extremely interesting fingerprint — and fingerprint technicians dusting the glazed magazine cover found the fingerprint of the burglar on the photograph of the fingerprint.

Spraying is probably the second most common means of testing for latents; on paper, it is the most common. A chemical called ninhydrin is the most widely used spray; its chemical name is triketo-hydrindine hydrate. Ninhydrin, available commercially in an acetone solution, has an extremely strong and unpleasant metallic odor; many technicians also dissolve it in amyl acetate—which gives it the smell of slightly overripe bananas—because some inks run, and some fabrics dissolve, in an acetone solution. However, the acetone is much safer; too much amyl acetate causes severe headaches ... and herein lies a story.

How not to develop prints on paper and cardboard:
The Albany ident section eventually grew to three people. The third was Robert "Butch" Windham. Although he'd entered the police department about the same time I did, he was far less experienced with fingerprints, and he was noticeably hardheaded. When we began using ninhydrin dissolved in amyl acetate, we all knew of its headache-causing properties, and Doc warned us that if we were going to spray more than one or two items we should take them out in the open air to spray.

One evening, on duty by himself, Butch decided to spray a large number of cardboard boxes. He took them out in the open air, all right—directly under the intake for the police department's air-con-ditioning system. By the time he got through, the building had been evacuated and the entire on-duty dispatch section was in the hospital. One dispatcher, who was several months pregnant, never did return to work. She was not harmed, but she was extremely frightened.

How to develop prints on paper and cardboard:
Although ninhydrin was developed in the nineteenth century as a specific reagent for amino acids, it was not applied to fingerprinting until 1954. Before that, iodine fuming and silver nitrate solutions were used to develop prints on paper. But iodine fumes are difficult to work with and extremely caustic, and silver nitrate, if not carefully controlled, will blacken the entire document.

When all three are to be applied, they must be used in this order:

• Iodine fuming

• Ninhydrin

• Silver nitrate (which may be sprayed or put in a dish for the document to be dipped in it).

However, most police departments use only ninhydrin. I have very rarely used iodine and never have used silver nitrate.

But iodine is essential in some espionage and other cases in which a document must be examined for fingerprints and then sent to its intended recipient, because almost always, iodine prints can be photographed and then treated with ammonia vapor so that they will completely fade out; in fact, they may fade out in the air unless they are sprayed with a fixative solution. Ninhydrin and silver nitrate are generally permanent, although manufacturers recommend fixing them also. (Both tend to be permanent on hands as well as on documents. Fingerprint examiners sometimes have very odd-looking hands. I suspect our lungs are pretty odd-looking as well; a fingerprint technician has to be totally away from work for more than two weeks before s/he quits sneezing fingerprint powder.)

Ninhydrin, as I mentioned, produces an unpleasant, acrid odor; however, as many as 50 percent or more of all fingerprint cases taken to court now involve fingerprints on paper, and at least 90 percent of those prints are developed with ninhydrin.

At times our lab resembled a laundry, with dozens of forged checks hung up on several small drying lines. It looked even funnier at the developing stage, when we started blowing the checks with a hair dryer.

Methods of Iodine Fuming

Prints developed with iodine are brownish-violet. Iodine fumes must be used inside a container; although commercial fuming tanks are available, an old glass fish tank with a light bulb in it to provide the heat to vaporize the iodine crystals is generally adequate. A sort of blowpipe, in which the technician's breath is blown through a fiberglass filter and over a handful of iodine crystals onto the paper, may be substituted. The paper must be watched carefully, as the prints develop quickly. The prints must then be photographed immediately, as unfixed prints will fade out almost as soon as they are removed from the iodine vapor. (Technicians use a special fingerprint camera, which produces a 1:1 ratio of negative to original — that is, a negative the same size as the original.)

Iodine works on oils from the skin surfaces that are transferred to the paper. (Fingertips do not produce oils; however, people touch their faces far more frequently than anybody but ident people realize, and oils from the face are transferred to the fingertips and hence to the paper.)

Methods of Using Ninhydrin

Ninhydrin is available in aerosol spray cans dissolved in acetone. Large-scale users can obtain it in crystal form; it is soluble in acetone or amyl acetate, and can be sprayed from plastic jars that use plain air rather than aerosol solutions as the propellant. The jars are slightly less efficient than the spray cans, but they are somewhat less expensive and probably safer for the environment. Dipping a document in ninhydrin dissolved in acetone is more efficient than spray cans or bottles, but it is also more likely to cause the ink to run. The spray form of this solution will not cause headaches, but if too much is sprayed in a small unventilated space, the user can wind up with chemical pneumonia. (I know. I did.)

Dipping a document in ninhydrin dissolved in amyl acetate will not cause the ink to run, and it is more efficient than using sprays, but it is far more likely to cause very severe headaches.

All of this means that each time ninhydrin is used, the user has to mentally weigh cost, efficiency, the need to keep the ink from running, and the possible health problems. These are all things you can use in fiction, especially if you're writing about a small department or a P.I. with a limited budget.

The prints developed with ninhydrin—which works on the amino acids contained in all perspiration—range in color from pink to purple. They develop in about twenty-four hours after the paper is sprayed, although some may continue to become visible for up to forty-eight hours after that. The stronger prints develop far more quickly under conditions of heat and moisture; we tried ironing them with a dry iron and with a steam iron, and later switched to the hair dryer, which worked very well.

However, one time we examined a check for the postal inspector and found no usable prints on it. The inspector then picked it back up from us and mailed it to the Postal Inspection Service Laboratory in Washington, D.C. Somewhere between our office and theirs the prints developed, so that when the check (properly packaged in a plastic sleeve so that no additional prints would be put on it) was removed from the envelope, the prints were quite clear.

Silver Nitrate in Developing

Silver nitrate, which reacts with the salt present in perspiration and hence in fingerprints, is used by dipping the paper in a silver nitrate solution or spraying the solution onto the paper. The paper is then exposed to normal light. It must then be watched extremely carefully, as it can go from clear black prints to entirely black paper in seconds. Once the prints have developed, the paper with the solution on it must be stored in absolute darkness, as every exposure to light recommences the darkening. Even paper that has been treated with a fixative will darken, although the darkening will be somewhat slower.

Other Methods of Fuming for Prints

Most people incorrectly believe that anything except paper is fingerprinted only with powder. Many other items, such as some plastics and all galvanized metal, are best treated by fuming. But these fumes don't come in a can. When I went through fingerprint school, I was told to burn a magnesium strip, which burns very quickly with a bright white flame and produces white smoke, to fume plastics and galvanized metal. Doc and I tried that exactly once and almost burned down the ident lab. We preferred fat pine (pine kindling wood), which produces a dense black smoke that liberally coats the item held above it. After the item has cooled, the excess smoke is brushed off with a normal fingerprint brush. There is no danger of brushing out these prints: The smoke actually fuses the print to the metal, and it's there forever. Sometimes, in multiple thefts from soft-drink machines, we got the coin boxes back to smoke two or three times and it got hard to tell which were the old prints and which were the new ones.

Fuming With Super Glue

The preferred fuming method now involves Super Glue. Yes, that's a trademarked product, and to start with that specific product was what we used. Since then, other products have been developed that work similarly, but most of the time, when a fingerprint technician says Super Glue, s/he means Super Glue. The glue is put onto a hard, nonflammable surface, and the item to be fumed is put near it. Then both are sealed into an airtight container. The prints, thick white in color, develop naturally in about forty-eight hours.

If more speed is needed, there are several methods of accelerating the process. One involves putting cotton balls soaked in sodium hydroxide near the Super Glue; another involves heating the Super Glue to about 200° Fahrenheit; and a third involves substituting a gel called Hard Evidence —a cyanoacrylate ester in a reusable sealed pouch—for the Super Glue. All have their advantages and disadvantages. Not only is Super Glue less pleasant to smell than fat pine, but also its use in this manner—which is
not
what the manufacturer recommends —can produce highly toxic fumes.

But it works on some extremely difficult surfaces. Probably there is no surface more difficult to fingerprint than a thin plastic bag, and Constable Garry Birch of Perth, Western Australia, was once faced with the task of printing 1,800 plastic bags that had been collected in a major drug raid. After some consideration, Birch acquired a large wooden crate used for overseas shipping. He then suspended the bags on strings draped across the container. He bought ninety-six tubes of glue and squeezed the glue onto three strips of aluminum foil, which he put on the bottom of the container. He then sealed the container for seventy-two hours.

Suspecting that much glue might have produced fumes nobody wanted to smell, he asked the fire department to open the container while using full breathing apparatus. After the fumes had dissipated, he examined the bags and found fingerprints on thirty of them.

Seventy-two hours may seem like a long time to wait for results. But if Birch had tried to dust with magnetic powder or photocopier toner, the only other reliable means of getting prints from thin plastic bags, he'd probably have spent a lot more time and might well have gotten worse results.

Technicians Steve Rowley and Bob Braman, in Salt Lake City, once Super Glue-fumed an entire airplane. Another technician, telling me about it, emphasized, "It wasn't a real airplane; it was only a Piper Cub." I assured him that I consider a Piper Cub a real airplane—especially for this purpose.

Lasers and X Rays

Less common methods of looking for latents include lasers and soft-tissue X rays. The FBI first used lasers in examining for prints on highly difficult items, such as the inside of powdered rubber gloves (yes, that's what I mean: the gloves were coated inside with powder before wearing) and the sticky side of tape, in 1980. In that year alone, they located 215 prints by that method, which led to forty-five convictions.

The Tokyo Police Department pioneered in the use of soft-tissue X ray to get fingerprints of a perp from the skin of a victim. This complicated method is still not available to most police departments because of the narrow time window in which such prints can be obtained and the lack of equipment; in fact, I am not familiar with any department that routinely uses this method. But that does not mean that your super P.I. can't use it.

More common—though still quite rare—means of getting prints from the victim's skin involve either thin silver plates or unexposed, developed, fixed, high-gloss, resin-coated photographic paper. Remember that as recently as twenty years ago, technicians believed that it was impossible to get prints from the victim's skin— although the materials with which this work is now done were already available.

Latents From Human Skin

Thin silver plates are given an extremely high polish using jeweler's rouge; the photographic print paper is cut into usable sizes, and then both are used approximately the same way. Both require several factors:

1. The victim's skin containing the print must be relatively dry and hairless. Hairy areas or moist, sweaty areas will not hold prints. Usually the only areas meeting this description are breast or abdomen skin or the inside of the wrist and upper arm.