Where’s your evidence? DNA, fingerprints and expert witnesses

Evidence collection has evolved significantly over the years. During the early 1900s, for instance, fingerprinting was a new technology that allowed law enforcement investigators to link individuals to crime scenes and provided them with real physical evidence that could be used in court to gain a conviction. DNA profiling is much more recent and was first introduced in 1984 by Dr. Alec Jeffreys, an English researcher studying the patterns found in various human DNA strands. For both types of evidence, enlisting the help of a qualified expert witness to explain the results can provide added help for attorneys in presenting their cases effectively.

Fingerprinting and classifications

In 1880, Henry Faulds first made the case that fingerprints could be used to identify suspects in criminal cases. This theory was published in Nature, a major scientific journal of the time. Faulds’ theory went unremarked for many years and was eventually appropriated by Francis Galton, a cousin of Charles Darwin and an unashamed plagiarist who based his own forensic theories on Faulds’ work without ever giving proper credit to his source. Galton developed a system by which fingerprints could be classified and distinguished. This method was soon superseded by more intuitive systems that were adopted by Scotland Yard and other law enforcement agencies sometime in the early part of the 20th century.

DNA and the RFLP test

Although James Watson and Francis Crick are often credited with the discovery of deoxyribonucleic acid, better known as DNA, the real honor should be given to Dr. Friedrich Miescher of Switzerland. Dr. Miescher isolated DNA from wound dressings; Watson and Crick were primarily responsible for identifying the double helix, a double-stranded DNA molecule. There is no such controversy, however, regarding the innovator who made DNA testing possible. Dr. Alec Jeffreys developed a test that could distinguish individuals from each other based solely on their DNA patterns. The restriction fragment length polymorphism (RFLP) test required a large sample of DNA from each individual for comparison purposes, making it relatively impractical for use in criminal investigations.

Polymerase chain reaction testing

Although polymerase chain reaction (PCR) tests had been around since 1984, it was not until the latter part of the decade that these processes were applied to DNA. PCR testing offered significant advantages over RFLP in practical use:

  • PCR tests can identify matching patterns using much shorter strands. This allows the evaluation of older DNA samples that may have been degraded or have broken down over time.
  • Less material is required to make a valid comparison using the PCR testing method.

Forensic scientists can provide valuable testimony and evidence regarding the likelihood that a particular individual was at the scene of a crime or that they committed incriminating acts.

Today, mitochondrial-based testing offers even greater pinpoint accuracy in determining whether two sets of DNA match up. For attorneys, obtaining testimony from expert witnesses with experience in fingerprint and DNA evidence can offer added support for a particular version of events. Remote depositions from acknowledged experts in these fields can be of benefit to both the prosecution and the defense in presenting their cases to judges and jurors in the courtroom setting.