Fingerprints are the oldest and most recognized form of personal identification used in law enforcement. More crimes have been solved through fingerprint identification than by any other means. As previously discussed, however, identifiable fingerprints seldom show up on firearms or ammunition. This can be problematic because juries expect fingerprints to be present whenever firearms are involved in crimes. Television and movies have perpetuated the myth that fingerprints will be found on every surface. For instance, in one episode of a television show that featured a seemingly inept detective who always solved cases in a brilliant fashion, the murderer had worn latex gloves to avoid leaving fingerprints at the scene. The detective solved the case by cutting the gloves open and dusting the inside surfaces with ground-up pencil lead, revealing the killer's fingerprints inside the gloves.
Although the real world differs significantly from Hollywood, fingerprints still provide a very important means for reconstructing crimes. First and foremost, fingerprints put an individual at the crime scene. Nevertheless, it must be remembered that not finding fingerprints cannot be interpreted to mean an individual was not at the scene.
Second, fingerprints can put an individual in a particular position or location at the scene. This can be the difference between being found guilty or innocent of a particular crime. Suppose, for example, a person has been accused of striking and killing another person with a bat based on the presence of fingerprints on the bat. The suspect offers the explanation that he had touched and moved the bat after finding it lying across the chest of the dead man but steadfastly maintains that he was not the killer. If the fingerprints are in a position to support touching but not holding, then that would be a huge part of his defense. On the other hand, if the fingerprints are more consistent with holding the bat than merely touching it, the defendant would have a big problem.
Fingerprints can put a person behind the steering wheel of a vehicle, put a knife in someone's hand, prove that they were on the floor at some point, suggest that they opened a drawer, and on and on. As long as the identification is valid and the individual has no legitimate reason to have been at the scene, the evidence is irrefutable.
Criminal investigators frequently use fingerprint evidence as a ploy to gain confessions from people they are interrogating. This tactic has been used successfully many times. The suspect is brought into the interrogation room and confronted with a question, such as "How did your fingerprints get on the murder weapon?" Suspects who have something to hide frequently fall for the ruse and start talking. The Supreme Court has ruled that police agencies may legitimately use deception to gain confessions.
The general knowledge that fingerprints are so incriminating often results in criminals making statements to investigators as to why their fingerprints will be present. In a highly publicized murder case in the Dallas, Texas, area, a woman had called 911 to report that her two young sons had been stabbed by an intruder. As she spoke to the 911 operator, seemingly hysterical, she mentioned that she had touched the murder weapon and that her fingerprints "would probably be there," a strange thing to be concerned about as her two sons lay dying. The jury may have perceived her remark as an attempt to cover up her crime. In any event she was convicted.
The general knowledge that fingerprints help solve crimes has also prompted individuals to wear gloves while they commit crimes to make an effort to wipe away the telltale evidence. What criminals may not know is that gloves with textured finger surfaces can themselves be identified. This is because the finger surface texturing is typically random in pattern, meaning that the pattern will not be exactly the same for another finger on that glove or for another glove, as with fingerprints. If the gloves are found in the possession of a suspect and the glove prints can be identified to a particular finger of a glove, this situation can actually be more incriminating than the presence of fingerprints, because it shows intent to cover up the crime on the part of the defendant.
Likewise, wipe marks can tell a tale. Suppose a person wipes down a gun or the inside of a vehicle in an effort to destroy any prints inadvertently left behind. Even though no fingerprints can be developed, the wipe marks are usually visible when fingerprint powder or superglue fuming is used on the surface. Sometimes a fabric pattern is left, and a fabric pattern can, in rare cases, point to a particular type cloth that was used. If a suspect happens to have such a cloth in his or her possession, that provides circumstantial evidence.
In conclusion, fingerprints can and do play a vital role in the reconstruction of crimes. Finding fingerprints on weapons, especially when there is no legitimate explanation for their presence, essentially puts the weapon in the perpetrator's hands. Unfortunately, however, there is no scientifically valid means of establishing when fingerprints were deposited on a surface. Studies, as well as casework, have shown that fingerprints left on surfaces years earlier can still be found. Thus, defendants can argue that fingerprints were left long before the crime. This argument goes by the wayside when there is no legitimate reason for their fingerprints to be present at all.
The case study that follows illustrates how the combination of fingerprint identification and firearms examinations work together to facilitate the reconstruction of a crime. This case is especially interesting from the fingerprint standpoint because it is a rare example of identifiable fingerprints being present on a firearm. The firearms aspects that this case will illustrate include bullet and cartridge case identification to a specific weapon as well as trajectory analysis and gunshot residue testing. The implications of criminal investigative efforts are also illustrated.
The reconstruction of a crime must consider the implications of information derived from the investigative efforts of the lead officer in a criminal investigation along with the results of field and laboratory testing relating to the physical evidence. It is important, for example, for the individual who is reconstructing a shooting incident to have any information that might establish a motive. Without a motive for homicide or suicide the evaluation of a possible accidental shooting takes on added importance. On the other hand a clear motive for homicide gives the examiner an initial area of concentration with regard to the physical evidence. All this must be tempered with extreme care to avoid "tunnel vision" and jumping to conclusions.
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