How to Catch Criminals by Their Choice of Lipstick with Chromatography

Scientists from Western Illinois University have developed a technique which could help police in the search for crime suspects. Although the method is in the early stage, the team hope that they will soon be able to take samples from any crime scene — a mug, a shirt collar or other incriminating spot — then use gas chromatography to analyse it.

In the past a lipstick stain at a crime scene could only give limited information about the cosmetics the suspect may have worn — unless the police resorted to expensive and complex techniques. This new method uses simple techniques and will let the police know the exact brand and style in a cheaper and more timely manner — helping them to quickly get a profile of the suspect.

Like taking lipstick from a coffee cup

Fans of shows like CSI or Cold Case will be familiar with tell-tale signs at a crime scene — fingerprints, bullet cases and lipstick stains — which can apparently be analysed in minutes, providing valuable leads to the investigation. The reality is that it’s far more time-consuming and expensive than depicted in forensic crime series.

‘Working on this investigation has opened my eyes to the fact that TV has it wrong — things take much longer in real life,’

explained Bethany Esterlen, lead researcher on the project.

Over the years, scientists have developed a number of complex ways to analyse evidence such as lipstick stains, as discussed in this article A Novel Tape Lifting System for the Retrieval of Trace Evidence From Crime Scenes. However, some of these techniques involve expensive instruments and need specially trained staff.

Esterlen and her team worked on a method to lift the lipstick samples which simplified the process and eliminated unnecessary steps. In their final process, they remove the majority of the oils and waxes found in the sample with an organic solvent — before using a different more basic solvent to extract whatever is left. In this way, they can quickly and effectively prepare the sample without losing any of the evidence.

Chromatography picks the lipstick brand

After securing the sample, Esterlen and her team then worked on determining which was the best approach to analysing it. After testing both high performance liquid chromatography (HPLC) and thin layer chromatography (TLC), they concluded that gas chromatography (GC) was the most effective technique of determining the specific chemical makeup of the cosmetic.

The researchers tested out 40 different lipsticks using the technique and have begun to compile a database of the exact chemical makeups of known brands. As their lipstick library grows, police should theoretically be able to determine exactly which kind of lipstick was used by a suspect at a crime scene — if a lipstick sample is found. By checking whether or not the suspect uses that particular brand, the prosecution might just have another piece of evidence in the case.

So, remember the line “GC is a better method” next time you’re watching CSI with your friends.

Image from Pexels