Does a Lack of Fingerprints Exonerate Oswald?

They point, for example, to the lack of clear fingerprints on Oswald's Mannlicher-Carcano rifle as evidence that Oswald, if he shot at Kennedy, would have had to "wipe down" the weapon to remove prints. Supposedly, he would not have had time to do this and make it down from the Sniper's Nest to the second floor where he encountered Officer Baker about 90 seconds after the shooting.

Unfortunately, among professional fingerprint experts there is no presumption that handling a weapon will leave any usable prints.  Consider, for example, the following statement by Alan McRoberts of the Los Angeles Sheriff's Department Scientific Services Bureau — Identification Section:
 

Often, detectives are disappointed and prosecutors are frustrated with the lack of the irrefutable evidence of the "suspect's" fingerprints on a particular item of evidence, which he must have handled. It is unfortunate that, unlike on television, the suspects prints don't always appear. A look at the factors influencing the chances of obtaining prints will assist in understanding the fragile and elusive nature of latent impressions. Each of the following various factors independently or in combination can account for the lack of prints on a surface: 1) Individuals don't always have a sufficient quantity of perspiration and/or contaminates on their hands to be deposited, 2) When someone touches something, they may handle it in a manner which causes the prints to smear, 3) The surface may not be suitable for retaining the minute traces of moisture in a form representative of the ridge detail, and 4) The environment may cause the latent print to deteriorate. The most important fact dealing with the lack of fingerprints is that it neither suggests, implies, or establishes that any person did or did not touch the item of evidence. Items which have been witnessed to have been handled and laboratory experimentation repeatedly reiterate this premise.

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When a report reads "no prints," what does that really mean? It means no prints of evidentiary value were preserved. It does not mean that the item was wiped down, or that no one had ever touched or handled it. Occasionally observations to establish that the item has been wiped down may be made and reported, but it usually would not be possible to determine at what point it was wiped or even if the item had been handled since the wiping. The term "no prints" does not mean that there were no marks or smears — it means that if any markings were present, they lacked sufficient detail to be of evidentiary value. As there are limits to the collection of prints at all scenes, an evaluation of what should be preserved as evidence is a necessity. Technicians cannot develop, preserve, document, and collect all fragmentary portions of ridge detail at crime scenes. Realistic expectations and a point of diminishing return are factors with which to reckon. ("Fingerprints: What They Can & Cannot Do!," The Print, Volume 10, number 7, June 1994, pp. 1-3. Emphasis in original)

A survey of prospective jurors done by Sgt. Charles Illsley of the West Utah Police Department included questions dealing with fingerprint testimony. When asked where these jurors acquired most of their knowledge about fingerprints, 58 percent listed television as their primary source, followed by newspapers, radio, books, and other sources. Frequently, crime scene technicians and lab personnel feel compelled to compete with the “Quincy's” of TV and the technology of “James Bond,” all within the time frame of “Sixty Minutes.”

Although most police personnel and prosecutors are aware of the factors relating to fingerprint identifications, some myths and fallacies — many perpetrated by the media — still linger.

Myths and Fallacies:

NO LATENT PRINTS WERE FOUND AT THE SCENE, SO HE MUST HAVE WORN GLOVES OR HE WIPED THEM OFF!

There are many factors that cause an item to lack sufficient ridge detail. Surfaces, pressure, or the condition that existed before or after the finger or hand touched the surface, are some of these. If the background where the latent print is found is rough, grooved, or textured, it may impede the continuity of the ridge detail in the latent print. For example, take a plastic baggie in your hand and make a fist. Releasing the bag in your hand you will notice the baggie unraveling. The ridge detail originally connecting in its compressed state will lack this continuity in the unraveled state. The amount of pressure applied to the surface has varying effects. The results differ drastically when the items, say, papers, were “grasped or rifled” through.

Again, the examiner does not always know the conditions that existed before or after the latent print touched the surface, but understanding the factors affecting latents aids the technician in explaining the fragile nature of these prints.

Weather conditions may be a contributing factor in the lack of prints. In cold weather, the pores that exude perspiration tend to close. In hot weather, the opposite is true — too much perspiration causes the recordings of the prints to be spotty and distorted. The ridges must contain some sweat, grease, oil, or other foreign matter or no latent print will be left on the item that was touched.

A large percentage of latent prints are “lost” before they are received at the lab for analysis because of poor handling or packaging of items to be examined. Most crime labs readily dispense information and assistance to police who may be having difficulty or problems with evidence retrieval.

THERE WERE NO FINGERPRINT IDENTIFICATIONS OF THE SUSPECT — THEREFORE HE DIDN'T DO IT!

The assumption is that if no fingerprints of the suspect were found, he is innocent. For the reasons mentioned earlier, he may not have left behind any identifiable prints linking him to the crime, but it would not necessarily eliminate him as a suspect. There may have been fragmentary ridge detail indicating the item was handled but not enough to make a comparison. In some instances, an object can be so heavily handled that the ridges overlap, preventing the examiner from determining which ridges belong to which latent print.

You may also be in a position to see the item being touched in, for example, a drug investigation where there is a "hand to hand" buy. You, as the agent making the “buy,” know the subject touched the bag when it was handed to you. Yet, when the bag is processed, the results may be negative. Lack of fingerprint evidence does not assume innocence. ("Separating Fingerprint Fact From Fiction," Law Enforcement Technology, January 1992)

Latent fingerprint examiners generally know that even when cutting-edge technology such as cyanoacrylate fuming and laser/forensic light source examination are utilized, successful development of latent prints on firearms is difficult to achieve. In reality, very few identifiable latent prints are found on firearms, a fact that has been discussed in both the literature and the judicial system. Fingerprint Specialists at the Bureau of Alcohol, Tobacco and Firearms San Francisco Laboratory Center have had, however, some success in this endeavor.

In the examination of 1,000 firearms from February, 1992, through August, 1995, 114 identifiable latent prints were developed on 93 firearms. Although successful recovery occurred in approximately one of ten firearms, it should be understood that not all identifiable latent prints may have been left by an offender. Some developed latent prints, for example, are subsequently identified as belonging to a person involved in the collection of the evidence.

Jurors have been inundated with fingerprint information from television, movies and newspapers and feel that latent print evidence is a reliable means of establishing positive personal identity. However, jurors are generally under the impression that every item that is touched by fingers or palms will be left with an identifiable latent print impression. If an offender is arrested for possession of a firearm, jurors therefore expect his/her prints to be on it. In fact, most of the time, fingerprint specialists find no identifiable latent prints on firearms.

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Summary

There are a number of factors that affect the fingerprint specialist's ability to recover identifiable latent prints on firearms. These are: the longevity of a latent print due to how it was deposited; atmospheric and environmental condition; perspiration variation; the nature of the firearm's surface and finish; how the firearm was handled; and packaging. Due to the reasons stated in this article it is difficult to obtain identifiable prints from firearms, but since in the experience of the authors it occurs almost 10 per cent of the time, the attempt should be made.

It is important that fingerprint specialists be able to describe the reasons why, despite their training, experience and access to state-of-the-art equipment, identifiable latent prints are developed on firearms infrequently. ("Factors Affecting the Recovery of Latent Prints on Firearms," Journal of Forensic Identification, Volume 47, number 2, April, 1997, pages 140-148.)

Sometimes these issues bubble to the surface in a high-profile criminal case. In 1973 H. Rap Brown, violent black militant, and three cohorts came to trial on charges of armed robbery and attempted murder that resulted from their robbing a bar on New York City's West Side and engaging in a shoot out with police who came to the scene of the crime.
 

A police expert testifying at the trial of H. Rap Brown said yesterday that it was virtually impossible to obtain usable fingerprints from firearms.

Sgt. William Torpey, who has been assigned to the Crime Laboratory for 18 of his 19 years on the force, was called to the stand by Assistant District Attorney Jack T. Litman in State Supreme Court.

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The prosecution apparently introduced yesterday's expert testimony in anticipation of a defense challenge that would ask why it had not introduced fingerprint evidence linking the defendants to the various weapons that are already in evidence.

Sergeant Torpey testified that during his 18 years at the Police Crime Laboratory he had examined more than 500 firearms for fingerprints and had found only one identifiable print.

Even when the fingerprints are found on firearms, sergeant Torpey said, they are almost always too smudged to be useful. One reason, he said, is that these weapons are likely to be slightly oily, especially if well kept.  Another is that the person using the weapon holds it so tightly that the prints are smeared.

And if the weapon is fired, he added, the jolt smears any prints that might otherwise have been useful. ("Brown Trial is Told Weapons Don't Give Usable Finderprints," New York Times, March 13, 1973)

Jean Davison and John Leyden supplied the sources used on this page.