an investigator will often use a black light to scan an area for traces of bodily fluids left at the crime scene. if there’s a substance that resembles semen or blood, they will often times apply a spray if it is dry and use a cotton swab to collect it in a vial to test back at the lab for dna evidence.
if to animals fight, the one more adapted, prepared or psychically built will win will the weaker one lose and die, which is natural selection at its finest.