Question: how would you work out who committed a crime if two people had the same makeup?

Katy Bruce answered on 12 Nov 2019:

Now that’s a good question and one I’m hoping to answer during the course of my research! The chances of two people wearing the same make up is quite high as millions of people wear it on a daily basis and there aren’t millions of different options. In this case we would look at association rather than the sample itself, I.e. how likely is it that THIS sample would be found in THIS context? Is it consistent with your expectations? Could it belong to someone associated with the scene? Is it located in an usual place? If a crime scene sample and reference sample were found to be different then it eliminates a suspect which can be just as important as finding a link.

Unfortunately, some questions can never be answered with a degree of certainty. In forensics we tend to rely on elimination rather than matching and we are taught never to state that two things match with 100% certainty…a judge would pull you apart in court if you said that!