As writers, we often take dramatic license and convince ourselves that the reader or audience isn't going to know the difference. Not true anymore. Crime readers and TV and movie audiences are getting pretty sharp and will pick up on sloppy crime writing. It takes a little longer, but getting it right is well worth the effort-for your sake, as well as for the people reading or watching your story. Ballistics is the study of the trajectory of a bullet, not the identification of the gun the bullet came from.
Criminology is the scientific study of crime and criminals.
A criminalist is a specialist in one of the forensic sciences. Bodies are seldom outlined in chalk or tape because they may have to be rolled over. Chalk markings or tape may be used when the victim is found outdoors, when someone has been struck by a vehicle, or when the victim has fallen from a great height. If the suspect refuses to be questioned, there isn't anything the officer can do except detain the suspect while checking for outstanding warrants. Use the right police codes.