Crime Scene Chemistry

24th June 2015

Chemicals, Science

forensic science

When we think of dusting finger prints at a crime scene we tend to think of Sherlock Holmes kneeling down in a low lit room smoking a pipe with one eye gaping through a magnifying glass, slowly dusting away at the prints left behind by the soon-to-be-captured suspect. But, with the giant improvements in both the chemistry and scientific industry does this method still apply? Well, actually yes it does! That’s exactly what is used by modern forensic scientists at a crime scene to this day, minus the smoking pipe and tweed deerstalker cap. The truth is, crime scene investigation is still a long, slow and painstaking task, which makes it all that more impressive. But one element which has massively improved since the early 1900’s is the analysis of the evidence found at a scene once it has been taken back to the lab, this improvement can be pinned down to a few things, but chemistry is top of the list.

Crime scene investigation, particularly in a murder case, depends hugely on forensic science which then utilises methods  from chemistry and bio chemical analysis for all matters of evidence collected at a crime scene.

Blood analysis from a crime scene highlights the importance of chemistry in a crime investigation. The Kestle-Meyer Blood Screening test being one of the most popular and highly relied upon tests within the industry. The Kestle-Meyer blood test is an extremely sensitive way to test for blood on a texture, or, in the event of crime scene investigation, evidence. Kestle-Meyer is a phenolphthalein indication solution which is reduced before application, usually by reacting it with powdered zinc. The idea behind the test is that the the hemoglobin in blood catalyzes the oxidation of the phenolphthalin into bright pink phenolphthalein, this is usually a strong indication that there are traces of blood in the tested area.

Dusting for Finger Prints

The more ‘traditional’ and old school methods are still used and relied upon even with today’s technological advancements, one of these being the ability to dust for fingerprints at the crime scene and take away a sample for comparison and analysis with a database. This fantastic video from Liverpool John Moores University shows forensic science lecturer Phil Gilhooley explaining how to dust and detect fingerprints at a crime scene and what to look out for.

As Phil Gilhooley explained above, the main compound used to dust for fingerprints is an aluminium powder and a zephyr brush. This then reveals any finger prints that have come in contact with the area under investigation. In order to take the dusted fingerprint from the crime scene and pass it to forensics in the laboratory, a form of sellotape is placed over the dusted finger print, it is then removed and transfered onto a black piece of card, where it is carefully placed down and any air bubbles are removed, the finger print is then ready to be analysed back at a forensics laboratory.

Recent Development

Three days after we published this post, forensic scientists from Austria’s University of Salzburg announced they have developed a new method of determing for “establishing an exact time of death after as long as 10 days” according to the BBC. The method consists of measuring the breakdown of muscle protein in dead pigs over time, which is a much more accurate and reliable advancement from the current method of measuring the core body temperature, which only works upto 36 hours after death.

It was determined that there was a “huge lack of reliable methods”, said Dr Peter Steinbacher from University of Salzburg. He went on to say that analysing muscle protein degeneration even after the body had cooled down to environmental temperatures proved to be a very promising method. The news was annoucned at Society for Experimental Biology’s annual conference in Prague.

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