This achievement is obtained on Case 1 and it is missable.
For this achievement, you need to take a picture of the bruise on the victims arm. After that, the doctor will say that the victim might have had cancer. You then need to check the victims fingerprints and DNA in the lab. You will then need to find and process the chemical from the ceiling of the kitchen in the Superla Spa, you find out it's Asbestos. You then need to talk to Pete Baxa, to do this simply go to his Hair dressing salon and when he goes to identify the victim's body, talk to him there. You need to ask Pete Baxa if the victim had any reason to start the fire, present the asbestos and contradict his statement. The achievement will unlock after your conversation with him. You should do this as soon as possible because he can't be found later on in the case.