Fingerprint Analysis (Famous Cases) (World of Forensic Science)
Forensic investigators have been using fingerprint evidence as a source of identification of suspects for over a hundred years. Early work was by visual analysis of very obvious prints left at the scene of a crime. Modern forensic scientists now have a range of techniques for finding prints, cleaning up and enhancing print images, and rapidly finding a match from a database using computer technology. Fingerprint evidence is seen as one of the best types of physical evidence linking a suspect to an object or location or for establishing identity. Therefore, the forensic investigator will always search for fingerprint evidence at the scene of a crime and at related locations, such as a suspect's home or car.
A fingerprint is the pattern of ridges and related characteristics found on the fingerpads, the fleshy parts of the fingers used for touching and gripping. Each person's fingerprints are unique and stay unchanged throughout life. According to Sir Francis Galton, the nineteenth-century English anthropologist, the chances of two fingerprints being identical are as small as 64 billion to one. In over a century of forensic fingerprinting, no two prints have ever been found to be the same, even those of identical twins.
Skin is never completely dry or clean; grime, oil, and sweat on the fingerpads create fingerprints whenever a person touches something. That is why criminals, unless they are wearing gloves, leave fingerprints behind. If their hands are bloodstained, then they will leave bloody fingerprints behind, an example of a patent (visible) print. Plastic prints are fingerprint impressions made in a soft material like soap or dust. Latent fingerprints are invisible, but the forensic scientist can visualize them though special lighting or with the application of chemicals. Fingerprints have been recovered from all kinds of surfaces, even plastic bags. It would be very useful to be able to reliably detect fingerprints on human skin. So far, this been very difficult to do if more than two hours have elapsed from the time the fingerprints were made. Potential methods are being developed to recover fingerprints after longer time periods have elapsed.
A fingerprint found at the scene of a crime can be dusted with chemicals to make it easier to see and then lifted or photographed. It is then compared with the fingerprints of known offenders stored in a computer database. In the past fingerprints were classified according to the specific features that make up the unique pattern of each print. With computerized storage and retrieval systems, however, classification is not really necessary as the computer can readily scan and match the whole pattern of thousands of prints. The image of fingerprints found at the scene of a crime can readily be enhanced and clarified with scanning and digitizing technology. This means that even partial prints can be of value in identifying someone at the scene of a crime.
In 1892 Francesca Rojas, an Argentine woman, became the first person ever to be convicted on fingerprint evidence. When her two young children were found beaten to death, she tried to blame a man called Velasquez who vigorously denied the charge and, in any case, had a firm alibi. Investigator Juan Vucetich, who was intrigued by the relatively new technique of fingerprint analysis, found a bloody fingerprint on a bedroom door in Rojas' house. He sawed the portion away and then had the woman give an ink-print of her thumb. Even with only a basic understanding of fingerprint analysis, it was obvious to the investigators that the bloody print belonged to Rojas. She confessed to the crime when confronted, and admitted that she committed the murders to improve her chances of marrying her boyfriend, who was known to dislike children. Rojas was sentenced to life imprisonment.
The brutal murder in 1905 of Thomas Farrow, manager of a shop in Deptford, near London, and his wife Ann was to become a milestone case in the use of fingerprint analysis in Britain. Money had been taken and a thumbprint was found on the cash box. The Criminal Investigation Department (CID) had already built up a file of fingerprints of known criminals, but this print did not match any of them. A witness led the investigators to two brothers called Albert and Alfred Stratton. A match was found between one of the men and the print found at the scene. The court battle over the evidence was, however, lengthy. Much hung in the balance as it was the first time fingerprint evidence had been used in a murder case in Britain. After two hours of deliberation, however, the jury found the two men guilty and they were later hanged.
In 1910, Thomas Jennings was arrested on suspicion of the murder of Clarence Hiller in Chicago. The main evidence against him was fingerprints, and four experts testified at his trial. However, fingerprint evidence was still relatively new and Jennings brought an appeal questioning its admissibility. In a landmark judgment, the Illinois Supreme Court upheld the conviction, saying that fingerprints were indeed a reliable form of identification. Jennings was sentenced to death and executed on February 16, 1912. He was the first person in the United States to be convicted of murder on fingerprint evidence.
Fingerprint analysis also played a role in convicting the man responsible for an audacious theft. On August 21, 1911, Leonardo da Vinci's Mona Lisa was stolen from the Louvre Museum in Paris. There was a clear fingerprint on the glass that had protected the painting. Fingerprint pioneer Alphonse Bertillon spent many months trying to match the print to samples in his collection but to no avail. Two years after the theft, police arrested Vicenzo Perugia in connection with the crime. His prints matched those from the crime scene. Ironically, Perugia's thumbprint had been in Bertillon's collection all the time, but it was of his right thumb. The one left on the glass in the Louvre was from his left thumb.
Criminals soon realized that fingerprints could be used to convict them and took evasive measures. Some used gloves but others, like John Dillinger, a gangster who terrorized the Chicago area in the 1930s, went further. While on the run from authorities, he had a plastic surgeon burn off the outer layer of his fingertips with acid, in the belief that this would erase his fingerprints for good. A tip off put the FBI on Dillinger's trail, they confronted him and shot him dead. In the morgue, they discovered Dillinger's attempts to burn away his this fingerprints. He had not succeeded. Fingerprints usually grow back and, in any case, go down through several layers of skin.
Early fingerprint investigators had a tough job sorting manually through print records. Today, matching is accomplished with the aid of high-speed computers. The FBI began to automate print analysis in the 1960s with AFIS, the Automated Fingerprint Identification System. The AFIS computer scans and digitally encodes fingerprint records into a database. It can match a sample, either a ten-print set or a single or partial print, by searching the database. Early versions of AFIS searched hundreds to thousands of prints a second; now the speed is up to 500,000 prints per second.
One notable success for AFIS was catching Richard Ramirez, a notorious killer known as the Night Stalker. He had committed a number of brutal rapes and murders throughout Southern California between 1984 and 1985, entering victims' homes at night and cutting the phone line. He would shoot any men present before raping their spouse, often in the same bed where the corpse laid. His final crime involved a couple in Mission Viejo, where he shot the man and raped the wife. Fortunately, both survived and the woman saw Ramirez' car, while another witness got the number of the vehicle. The stolen car was found abandoned and a partial fingerprint was recovered from the vehicle. The Los Angeles Police Department had just begun to use an AFIS system that could compare more than 60,000 prints per second and they found a match for the print in the car within minutes. A photo of Ramirez, a 25-year-old drifter from El Paso, went out in the papers and he was recognized within a day by residents in east Los Angeles, who overpowered him when he tried to steal another car. He was convicted by a jury and, on November 7, 1989, was given 19 death sentences.
Palm prints contain even more detail on them than fingerprints, and helped solve the kidnap and murder of 12-year-old Polly Klaas in 1993. The girl was enjoying a pajama party with friends at her home in Petaluma, California, when a man appeared through an open window with a knife and carried her off. The FBI used special light sources and fluorescent powder to locate an otherwise invisible palm print on a bunk bed. They also had a description of the intruder from the other girls. Torn children's clothing was found a few weeks later near a site where a man's car had rolled into a ditch. That man was Richard Allen Davis, who had two previous convictions for kidnapping. A fingerprint expert was able to match the FBI's palm print found at the scene of the crime to Davis, who then confessed and showed police where Klaas' body was. He was sentenced to death in 1996 for kidnapping and murder.
SEE ALSO Anthropometry; Fingerprint; Latent fingerprint; Ridge characteristics.