Crime on Mars is going to be… complicated:

Consider the basic science of crime-scene analysis. In the dry, freezer-like air and extreme solar exposure of Mars, DNA will age differently than it does on Earth. Blood from blunt-trauma and stab wounds will produce dramatically new spatter patterns in the planet’s low gravity. Electrostatic charge will give a new kind of evidentiary value to dust found clinging to the exteriors of space suits and nearby surfaces. Even radiocarbon dating will be different on Mars, Darwent reminded me, due to the planet’s atmospheric chemistry, making it difficult to date older crime scenes.

Rian van der Merwe The B-Sides