An article published in the Journal of Forensic Science details the fruits of a collaboration between the University of Leicester and the Northamptonshire Police, which led to a “major breakthrough” in crime detection, perhaps allowing “hundreds of cold cases being reopened,” according to a press release. The University’s Forensic Research Center has been working with Northamptonshire Police's scientific support unit to develop new ways of taking fingerprints from a crime scene. The collaboration between the boffins and bobbies – boffin being British slang for someone engaged in technical or scientific research, apparently, and bobby being slang for police – was formally launched May 14. (For those without an intimate knowledge of U.K. geography, Northamptonshire Police headquarters is located in Northampton, about 70 miles NW of London. The University of Leicester is another 40 miles or so northwest of Northampton.) The newly developed method enables scientists to visualize fingerprints even after the print itself has been removed, the press release said. According to the article abstract, ionic salts present in the fingerprint residue corrode the metal surface to produce an image of the fingerprint that is both durable and resistant to cleaning of the metal. The method can enhance a fingerprint that has been deposited on a small metal cartridge case before it was fired. (Researchers can heat the metal to approximately 600 degrees C [1112 degrees F, for the non-metrics out there] to simulate firing a weapon.) “Results are presented that show practical applications for the enhancement to fingerprints deposited in arson crime scenes, contaminated by spray painting, or deposited on brass cartridge cases prior to discharge,” the author, listed as Bond, J., but alas not James Bond (although that would have been really cool), wrote. John Bond is an Honorary Fellow at the University of Leicester and Scientific Support Manager at Northamptonshire Police. An electrostatic charge is applied to the metal of interest (a gun or a bullet, for example) which is coated with a metallic conducting powder. The powder preferentially adheres to the corroded part of the metal surface, thus exposing the fingerprint. “Wiping it down, washing it in hot soapy water makes no difference - and the heat of the shot helps the process we use,” Bond said in the press release. “The technique works on everything from bullet casings to machine guns. Even if heat vaporizes normal clues, police will be able to prove who handled a particular gun.” This means that cold cases could be reopened because unless a criminal scraped off a layer of metal while removing traces from his/her crime scene, the fingerprint will still be there. Other projects through the collaboration: how drug use affects an offender’s likelihood of being caught through forensic science analysis of the crime scene; and ways of identifying offenders by traces of their footwear. Offenders may vary the make and type of their shoes, but they are less likely to vary the price they pay for them, according to a report on the Northamptonshire police site. In a somewhat related note, a study from March 2007 noted that “conventional development of latent fingerprints is compromised when the prints are decomposed by extreme temperatures, such as those encountered when a weapon cartridge is fired, an improvised explosive device is detonated, and/or in arson cases.” Authors Richmond-Aylor, Bell, Callery and Morris wrote that understanding “how these extreme temperatures alter the chemical and physical properties of latent fingerprint residue could aid in the discovery of a reagent that could effectively develop these decomposed fingerprints.” Pyrolytic decomposition products showing the most promise were from alanine, maleimide and aspartic acid. Looks like the ol’ scotch tape method of fingerprinting has fallen in favor, while fancy spectroscopy and corrosive chemicals are all the rage. Interesting tidbits about fingerprinting, courtesy of the Northampton Police:
  • In ancient Babylon, fingerprints were used on clay tablets to confirm business transactions.
  • Thumbprints have also been found on ancient clay seals in China.
  • In 1911 Thomas Jennings became the first criminal to be convicted on fingerprint evidence. He was found guilty of the murder of Charles Hillier whilst committing a burglary in the United States.
  • Fingerprints are usually exposed by dusting with a light aluminum powder, after which they are lifted from the surface using a clear adhesive tape. The tape is then mounted onto clear plastic, sealing and preserving the print. Special staining techniques are used to reveal fingerprints on porous surfaces like paper, cardboard, or other difficult surfaces.
Two other interesting fingerprinting tidbits, from two recent e-publications (ahead of print) – one, a meta-analysis by Dror and Rosenthal estimate effect sizes indexing the degree of reliability and biasability of forensic experts. The analyses show that “experts are not totally reliable nor are they unbiasable,” the authors write. Two, Fields and Molina describe a novel approach to fingerprinting mummified fingers. Apparently the most common technique heretofore has been to amputate the fingers and soak and/or inject them with various solutions to enhance the fingers. The authors say their new technique produces a superior quality of print without amputation – they remove and rehydrate the fingerpads and then ink/roll them, using a gloved finger for support. That’s a relief, says mummified Pharaoh Tutankhamun, whose Jimi Hendrix cover band suffered precipitously after lead guitarist Rameses II lost the fingers on his playing hand to an archeologist last year.