What is Fingerprint evidence?
A fingerprint is an impression left on a surface by the friction ridges of an individual’s finger. Oil, moisture or perspiration on a person’s fingertip is responsible for this impression, which can then be ‘developed’ and ‘lifted’ for the purposes of identification. Fingerprints can also be obtained deliberately by transferring a substance (like ink) from the fingers onto an even surface. Prints are usually classified under three main categories – patent, latent, and 3-dimensional – depending on the surface on which they are found and whether or not they are immediately visible.
History of Use of Fingerprints as Evidence.
In 1911, the first criminal conviction involving the use of fingerprint evidence was recorded. During a failed home invasion, a man named Thomas Jennings shot and killed homeowner Clarence Hiller in South-Side Chicago. Jennings was apprehended later that night and, crucially, had left behind a fingerprint on a freshly painted railing at the Hiller residence. Police then photographed and removed the railing for use as evidence in his trial, which led to the successful identification of Jennings as the assailant by the court. Since this landmark case, fingerprints have been used as forensic evidence in cases around the world for more than 100 years.
How are they collected?
Latent prints are transferred to hard or level surfaces and are invisible, so they must be carefully developed before they can be examined. Typically, using soft brushes, a fingerprint technician will spread extremely fine powders or chemical reagents over the site of an impression. Such substances are intended to stick to the oils left by the finger. Once excess powder is removed, any fingerprint should be visible. It may then be photographed and ‘lifted’ using clear adhesive tape, preserving the print. Patent prints are similarly found on hard or level surfaces, but they are visible to the naked eye and are imprinted when a substance like blood or dirt is transferred from a finger. As such, the fingerprint may be obtained through photography. Soft surfaces like clothing present challenges to investigators, as special techniques and compounds are required to reveal the three-dimensional fingerprints that may be left on these difficult surfaces.
Using a fingerprint to identify an individual
Fingerprint identification is known officially as dactyloscopy, which is the process of examining and comparing separate ridge skin impressions to determine whether they came from the same person. This process of identification relies on matching the patterns of certain characteristics of a print and carefully comparing them to the patterns on another print. There are a number of key details that fingerprint analysts look out for, including ‘islands’, ‘dots’, and ‘ridge-endings.’ Forensic technicians will usually go through a rigorous procedure of analysis, comparison, evaluation and verification to arrive at a conclusion. The process can become quite complex – check out sources like the Australian Federal Police website for more information. https://www.australianpolice.com.au/dactyloscopy/fingerprint-identification/
Human fingerprints are very useful pieces of forensic evidence for a number of reasons. Chief among these reasons is that, insofar as the forensic community is aware, every human fingerprint is unique and prints are durable over a person’s entire life. They are also highly detailed and difficult to alter. This makes them excellent long-term identifiers for police, investigators and other authorities to utilise in their work.
Fingerprint evidence is very common in Australian court cases; in 2016, more than 10,000 fingerprint matches were made in Victoria alone. Generally, police will take a person’s fingerprint for identification and record-keeping purposes once they are taken into custody. Most agencies have an automated system which they then use to compare a fingerprint to all the samples that have been entered into the system. For this reason, it is common for repeat-offenders to be implicated in criminal activities by the fingerprint impressions they leave at the scene.
When should you hire an investigator for fingerprint analysis?
Our forensic investigators are able to determine whether or not fingerprints are readily apparent on a surface, as well as collect and analyse the evidence at a standard acceptable for use in a court of law. There are a multitude of situations in which fingerprint evidence is relevant, and the fragile nature of this type of evidence means it is wise to contact an investigator as soon as the need arises. Most often in criminal matters, a print may need to be lifted from things like drawers or lock boxes in cases of theft. Prints are also usually present on documents, clothes, and even defamatory or harassing letters from an anonymous source. Whatever the surface, once we are able to identify whether a fingerprint is present, we can get to work on identifying whether they belong to a particular suspect or group of suspects. In cases of criminality, we can provide the samples we obtain to the police to assist in their investigation. In any circumstance where an individual needs to be identified, our forensic experts are capable of endeavouring to assist in this way. As is the case for many other forms of evidence, fingerprint evidence may degrade over time so get in touch with us as soon as possible to discuss your matter.