Sunday, November 29, 2020

New modified fingerprint chemical that fluoresces touch DNA on clothing

Must read

FBI errors throw forensic convictions into question

Holding your hands up and saying "we got things wrong" is a difficult thing to do. But that's exactly what the FBI and US...

Canadian-Based Forensic Anthropologists are Helping Bring Closure to Guatemalan Genocide Victims

by Raf Katigbak, VICE From an outsider's perspective, the job of a forensic anthropologist can seem almost mundane. There's the practical side: the digging, the meticulous...

Terrorists Forging Fingerprints

Turkish counterterrorism units discovered a new tactic being used by Daesh militants during a raid in the Central Anatolian province of Kirsehir on Dec....

The Art of Crime

Lois Gibson, forensic artist for HPD, has helped catch thousands of criminals—and now puts her skills to use in unexpected ways. It’s crazy the things...
Michael Whyte
Crime Scene Officer and Fingerprint Expert with over 12 years experience in Crime Scene Investigation and Latent Print Analysis. The opinions or assertions contained on this site are the private views of the author and are not to be construed as those of any professional organisation or policing body.
- Forensic Podcast -

In sexual assault and burglary investigations, the recovery of DNA from items that have been handled by the suspect is very important. This is called touch DNA analysis and is a key technique in forensic investigations.

When examining clothing for touch DNA, traditionally the Forensic Investigator has relied upon CCTV footage or witness/victim testimony in order to target the correct area for sampling. This can often be a difficult and time consuming process and there’s no guarantee the examiner is targeting the correct area that will yield a DNA profile. It’s only after the sample is analysed that this confirmation is provided and if unsuccessful, the Forensic Investigator can target a different area.

What if there was a way to visualise exactly where the touch DNA is located on the clothing… What if it glowed under a florescent light source that it made it ideal to be photographed and recorded correctly. Well that’s exactly what these Japanese researchers reported on in their study published in Forensic Science International: Genetics.

The researchers developed a modified formulation of a fingerprint development chemical known as DMAC (p-dimethylaminocinnamaldehyde). The conventional DMAC method mainly develops fingerprints deposited on paper, thermal paper, and bills by heating with DMAC in a fume hood or placing the forensic sample between two sheets of copy paper that have been soaked in DMAC. To date, no method has been developed for spraying DMAC on clothing directly to visualise touch DNA from finger or palm prints that may have had contact with it. 

In the study, the researchers sprayed the modified DMAC solution onto clothing and left for 2 hours before visualising it under irradiation with a blue LED light (452nm). Not only were they able to visualise the touch DNA from where the finger and palm prints made contact with the shirt but they were also successful in obtaining DNA profiles from the target areas.

A latent finger and palm print was deposited on a T-shirt (100% polyester) for 10 s. The print was developed by spraying with DMAC solution and then visualized 2 h later with a 550-nm longpass camera filter under irradiation with a blue LED (452 nm).

The researchers concluded that that use of the DMAC solution and irradiation with a blue LED did not adversely affect the DNA extraction, quantification, or amplification processes for STR analysis.

The researchers want to investigate a larger variety of types of clothes and biological samples in future. However, their study shows that DMAC treatment of touch DNA on materials is useful for forensic investigations.

For more information about the research, in particular the formulation of the modified DMAC reagent;

Read the Paper Here

Development of a modified p-dimethylaminocinnamaldehyde solution for touch DNA analysis and its application to STR analysis, Forensic Science International: Genetics,

- Advertisement -

More articles

- Advertisement -

Latest article

Trees and shrubs might reveal the location of decomposing bodies

Plants could help investigators find dead bodies. Botanists believe the sudden flush of nutrients into the soil from decomposition may affect nearby foliage. If...

Are Detectives discounting the associative value of fingerprints that fall short of an identification in their investigations?

Every day, Fingerprint Experts in every latent office across the globe examine fingermarks that they determine to fall short of an identification....

Using the NCIC Bayesian Network to improve your AFIS searches

This National Crime Information Centre (NCIC) Bayesian network is based on the statistical data of general patterns of fingerprints on the hands...

DNA decontamination of fingerprint brushes

Using fingerprint brushes across multiple crime scenes yields a high risk of DNA cross-contamination. Thankfully an Australian study has discovered a quick and easy way to safely decontaminate fingerprint brushes to prevent this contamination risk and allows the brushes to be safely reused even after multiple cleaning cycles.

Detection of latent fingerprint hidden beneath adhesive tape by optical coherence tomography

Adhesive tape is a common item which can be encountered in criminal cases involving rape, murder, kidnapping and explosives. It is often the case...