Mass Spectrometry Being Studied as Way to Analyze Overlapping or Weak Fingerprints
by Anthony W. Accurso
Desorption electrospray ionization, a type of mass spectrometry (“DESI-MS”), is being studied as a way to analyze overlapping or weak fingerprints, solving an age-old problem of evidence quality.
For over a century since Scotland Yard established its first Fingerprint Bureau, the issues of overlapping or weak fingerprints have bedeviled forensics practitioners. While many movies and TV shows feature investigators who obtain fingerprints from a surface and then identify the culprit, whether someone is ever identified depends on the quality of the evidence. Samples can include two overlapping fingerprints or fingerprints that are barely visible, making them essentially useless.
Researchers at Aarhus University in Denmark have found that fingerprints samples collected using gelatin lifters, a relatively common tool for police departments around the world, can be analyzed using DESI-MS to enhance a weak sample or distinguish two or more prints in a sample.
“We are presenting a method that has the potential to be integrated into the police’s traditional workflow. If this happens, more fingerprints from crime scenes could be used and evaluated both visually and chemically,” says postdoctoral researcher Kim Frisch, lead author of the study. The process “works by measuring the chemical compounds in these collected fingerprints based on their mass.” An electrically charged solvent, usually methanol, is sprayed onto the sample. This causes the sample to “release and ionize,” where it is then collected into the mass spectrometer and analyzed for chemical composition.
Since the oils or substances on each person’s fingers are distinct enough, two overlapping samples can be distinguished. This can enhance weak fingerprints because chemical traces could be less than visible to the eye, but their chemical composition can still be analyzed. DESI-MS has been in use since around 2004 and used to analyze fingerprint samples collected on glass or tape. But gelatin filters “are suitable for lifting fingerprints from delicate surfaces, such as peeling wall paint, and irregular objects like door handles.”
The technique has limitations though, as it takes longer than standard techniques.
“The scanning process is time consuming, which means that we would not be able to analyze samples in the hundreds, as we do with, for example, blood samples. We expect that the method will be used in the future as a special analysis in more serious cases such as murder and rape,” said Frisch.
Source: forensicmag.com
As a digital subscriber to Criminal Legal News, you can access full text and downloads for this and other premium content.
Already a subscriber? Login
