That was my first thought, but I'm sure it a legal process that has to be conducted to provide official medical information when any trials take place. I was surprised to read this morning that the two murderers were shot by police. Unfortunately they're both still alive.
Unfortunately, in a criminal proceeding, the prosecution is required to document EXACTLY the criminal action done. In this case, measurements of the size and depth of wounds, marks indicating which weapon inflicted them, etc.
Additionaly, at least over here, it can ALSO be used as evidence of suffering inflicted as evidence for sentencing. . .