In addition to what others have said, angle of the stab wound is a determinant. The shape of the wound can indicate what position the victim was in when the attack happened, as well as the height and strength of the attacker, and even whether the attack was made with the left or right hand.
A lot of forensics is based in math. Forensic science can determine whether someone jumped from a building or was pushed, how tall a person is by the size and spacing of footprints, and more. It’s really a fascinating field.
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