Post-Mortem Bruising

Special Credit to Analytical Deduction

  First of all, just to cover my bases, bruising is typically caused when small blood vessels underneath the skin rupture. The pooled blood is what gives bruises their distinctive blueish hue.

So, in theory, post-mortem bruising would be nigh on impossible, because you would need the blood to be pumping in order to pool. And it is commonly regarded as extremely unlikely.

However, it is possible. It has been demonstrated multiple times that with enough force, a cadaver can bruise post-mortem. The rule of thumb is: 2-3 minutes after death, bruising can still easily occur. Up until about 3 hours after death, bruising is still possible, but it requires a fair bit of force. You would need to forcibly press the muscle or tissue against the bone. An example of this would be, say, dropping the body a short distance.

The best way to tell post- from pre-mortem is, unfortunately, through autopsy. They can determine the damage beneath the skin, and therefore match the amount of visible bruising with the damage or force inflicted upon the actual flesh. The option of cutting open a cadaver, however, is not really the most joyous prospect for some of us, though.