'I'm a how man, not a why man'.
Photographic examination is better than taking a plaster cast because plaster can expand when drying by between a half and full foot size. The depth of a footprint can indicate the weight of the person leaving the print. This can help in cases where someone uses a larger pair of shoes, for example a woman posing as a man or someone trying to set someone else up for a murder. Footprint depth can also show whether someone walks with a limp.
Dew and insects under a body give an immediate indication that it has been there overnight.
If a body is dragged it may collect leaves and dirt in unnatural places, for example in a collar or pocket.
High velocity bullets go straight through. Hunters tend to use them because they make a clean kill. The rounder the bullet the more tissue damage it will do. Hollow point bullets are particularly nasty and will do a lot of internal damage. Gunpowder leaves a residue trace on clothing and skin which can identify a killer and the test is fairly easy. We recreate this in our CSI event.