Jane Tennant's team routinely photographs the crime scene before allowing evidence to be touched or moved. Many times, however, a piece of evidence is picked up and handled before being photographed.
Even though they should be sending a large contingent of NCIS agents, police and/or other federal agencies to many emergencies, many times it is just Jane Tennant and her team confronting dangerous criminals and are often outgunned by the bad guys who have automatic weapons.