An arson and explosives expert, Horatio Caine left the bomb squad to take over the CSI labs after Megan Donner stepped down. He is haunted by the twin deaths of his Mother, who was killed by a drug dealer when he was seventeen, and his brother, Raymond, a Miami Dade narcotics officer who was abusing crystal meth at the time of his murder. Horatio often worries that his feelings for Ray's widow, Detective Yelina Salas, are going to cross the line, choosing to keep her at arm's length. Without a family or relationship, he is a tireless crusader for what he views as "his city", spending his off hours poring over scientific articles. As a three-dimensional thinker, Horatio is more comfortable on a crime scene than in the lab, always preaching that the cases aren't about him, but about the victims.

Known as "Bullet Girl" throughout the Miami-Dade Police Department, Calleigh is a top drawer ballistics expert who can ID calibers on sight. Her path may have been predestined - the product of a "shotgun" wedding, she was raised in a "shotgun" shack by alcoholic parents - despite carrying the name of a once proud Louisiana family. An early teen delinquent, she was able to put her past behind her and make her own name by being the first in her family to attend college, receiving a full ride scholarship at Tulane. Her thirst for knowledge and enthusiasm for firearms quickly took her from walking a beat on the streets of New Orleans to the Crime Labs of Miami.

Having come up through the crime labs under the tutelage of Megan Donner, Tim Speedle often serves as Horatio's "go-to" guy within the department. As the resident trace evidence expert, he has a keen eye for detail, seeing things that no one else can. Despite this, his approach is frequently intuitive, trusting his gut just as much as the evidence. He enjoys his seniority over Delko, often forcing him to do the "dirty" jobs, while he returns to the lab to review evidence. Although he is something of a lady's man, Speedle prefers to blow off steam by cranking Lynyrd Skynard, and hitting the streets on his Ducati racing bike.

The newest member of the CSI team, Delko is a first generation Cuban, having crossed the Florida Straits while still in his Mother's womb. Upon arrival, his Russian born Father changed the family name from Delektorsky to Delko, and christened his newborn son Eric. Delko is a natural athlete, having graduated with a swimming scholarship from the University of Miami. After realizing his dreams of Olympic gold would never be realized, he turned his attentions to the police academy, and to his Father's disappointment - offered his skills to the MDPD underwater recovery department. Delko was Horatio Caine's first appointment upon taking over the crime lab, having been impressed with the younger man's skills during a bomb scare. Despite his freewheeling nature - his love of the nightlife and fast cars - he is an invaluable asset to the team with strong ties to Miami's Cuban-American community.

After being wrongfully blamed for the death of a patient, Alexx Woods found her medical career sidelined, forcing her to seek out part-time work in the coroner's office. Unexpectedly, she took to her role with a unique sense of drive and purpose. Her job is to speak to the dead, to soothe their pain, and listen to what their bodies "say" to help bring their killers to justice. She is meticulous in her work, and is frequently accused of being compulsively tidy by her husband and two sons. She is most comfortable keeping to herself in the lab - but is still seen as a crucial member of the CSI team.

TThe widow of Raymond Caine, Detective Yelina Salas now finds herself in the awkward situation of serving as the departmental liaison for her brother-in-law Horatio and his CSIs. She is aware of Horatio's attraction to her, and often tries to steer him into spending more time with her and her son, Raymond Jr. - but Horatio always insists on keeping his distance.