The viewers are introduced to two homicide detectives, a senior detective (usually a veteran cop) and a junior detective (usually a young but capable detective), who report directly to their boss at their precinct (either a Lieutenant or a Captain). When they first arrive at the crime scene they are met by the first responding officer or a Crime Scene Unit (CSU) forensic technician, who will inform the two lead detectives on everything known at that point. It's during their preliminary crime scene examination that the featured detectives will make their first observations and come up with some theories followed by a witticism or two before the title sequence begins.