Character Name: Danny Messer
Character Face: Carmine Giovinazzo
Job: CSI Level 3
Rank: Detective Third Grade
It has been implied that Danny (rarely referred to as Daniel) Messer grew up on Staten Island (like the actor), in a family of law enforcers and law breakers (as is suggested in the episode "Tanglewood"). As a result, he formed his own set of hybrid ethics, seeking justice where it can be found. His badge number is "8946".
Though very little is known about the Messer family, Danny openly admits that he has had a rocky relationship with his older brother, Louie. Despite the strained relationship, Danny would come to lend money to Louie on more than one occasion (episode 211, "Trapped"). It is later learned that the brothers' relationship was permanently scarred by the events of a single night in 1991. After promising to take Danny to Atlantic City with some of his friends, the group stopped off at Giants stadium where Louie and two others began to severely beat a drug dealer, telling him it was an initiation into the Tanglewood Boys gang. When Danny protested, Louie called him a disgrace and told him to leave. It was later revealed that Louie deliberately sent Danny away to prevent any involvement in the subsequent murder of that drug dealer (episode 220, "Run Silent, Run Deep"). Due to Danny's DNA appearing on an old cigarette butt at the crime scene, Mac is forced to temporarily revoke Danny's badge until Danny is proven innocent. Though hurt, Danny understood why and obliges without complaint. The cold case is eventually solved, but Louie is beaten into a coma by the remaining members of the Tanglewood Boys. Danny is shown explaining that he finally understands Louie's actions. Later, Danny tearfully admits his grief and remorse to Mac.
Although Danny and his older brother grew apart in their teenage years, it can be said that they were close as children, since Danny fondly recalls rowing in "the bay" with his brother in their grandfather's boat to dive for bottles (episode 402, "The Deep"). He goes on to say that on one occasion their boat drifted into the harbor, and they were taken home by the Coast Guard, much to the dismay of their mother who, in turn, didn't speak much to her youngest son for a week thereafter; he describes it as "the quietest week ever."
After breaking his wrist in a fight as a young man, Danny left his growing baseball career, and entered the NYPD Police Academy, graduating first in his class (episode 122, "The Closer"). Despite this, because of his volatile personality, and possibly his history on the sidelines of the Tanglewood Boys gang, he was considered a bad fit for the CSI lab, and Lab Supervisor Mac Taylor was strongly cautioned not to hire him. Mac's decision to take him on is an honor and a responsibility that Danny attempts to live up to each day.
Danny has displayed a tendency to follow his intuition when solving a case, rather than relying on the evidence, for which Mac has criticised him (episode 105, "A Man a Mile").
Some people regard Danny as a playboy, seemingly aware of his good looks and charm. The possibility of having multiple girlfriends is alluded to (Episode 113, Tanglewood) when Aiden assumes Danny has visited a so called rub-and-tug kind of massage parlor he replies "You kidding me? I got girlfriends for that, why would I pay?" During a case they worked together, Stella catches Danny checking out the waitresses in a trendy Japanese restaurant in which food is served off the bodies of nude serving women (Episode 104, "Grand Master)". When Stella comments about the sanitation of this kind of dining Danny replies, "Who cares if it's sanitary? I wanna see the menu." In season 2 (episode 210, Jamalot), he is seen to be dating a woman named Cindy; in the episode, his phone rings, showing her name while playing a Coldplay song, and Danny states, "It's called "Talk" -- something my girlfriend is really good at."
In Season 1, Danny and fellow CSI Aiden Burn were shown to have a very close relationship as friends who routinely flirt with one another. In season 1 episode 19, Danny and Aiden work a case during which he catches Aiden behaving flirtatiously towards Officer Lilly, the first officer on the scene, and, back at the lab, teases her about it. Aiden tells Danny that he's cute, but she's way out of his league, which he takes in good humour. In the late Season 2 episode "Heroes" (episode 223), Aiden, who had been fired from the crime lab earlier in the season, is found brutally murdered. Danny is by far the most shaken member of the team, and lashes out at a man brought in for questioning for Aiden's death. When he begs Mac to let him interrogate the man, Mac refuses, knowing Danny is likely to become violent out of grief. After catching Aiden's killer, a rapist named D.J. Pratt, who Aiden had been intent on bringing to justice, Danny and the rest of the team meet at a local pub and toast their lost friend and colleague while reminiscing about her, knowing that they have fulfilled their promise to put Pratt behind bars for his crimes.
Danny initially indulges in some friendly team hazing of Lindsay Monroe, the detective brought in from Bozeman, Montana, at Mac's request to fill the gap left by Aiden's dismissal. On her first day, Danny tricks Lindsay into calling Mac "sir," a title that Mac has always hated (episode 203, "Zoo York"). Lindsay resents this incident, and over the course of the next episode they are both stand-offish in their interactions. They soon come to respect each other professionally and develop a friendship. For the remainder of Season 2, their relationship is one of friendly competition and playful banter which is obvious even to their coworkers; the coroner Sid Hammerback tells Lindsay that Danny calls her "Montana" because he has a crush on her (Episode 222 "Stealing Home").
In episode 302, "Not What It Looks Like," Danny's deepening feelings towards Lindsay manifest themselves almost by accident. He voices his concern when Lindsay volunteers to go undercover and walk into a hostage situation, and, when she is rescued by the team, she is the first person he looks for, checking her for injury and holding her close. In the following episode, "Love Run Cold," he is shown to have asked her on a dinner date, for which she never appeared, offering only an apology afterwards. Later, she admits that she shares his feelings, but that she needs time alone to put some things behind her that she thought she had dealt with. Lindsay's withdrawal in this and subsequent episodes is later revealed to be due to renewed grief from having been the sole survivor of an attack, as a teenager, during which several of her friends were murdered by a man named Daniel Kadence.
In episode 318, "Sleight Out of Hand," Danny works multiple shifts while Lindsay returned to Bozeman, Montana to testify at Kadence's murder trial. After Mac sends an exhausted and borderline-delirious Danny home, Danny makes a spur of the moment decision to fly to Bozeman. He arrives at the courthouse while Lindsay is on the stand. His presence gives her the confidence to finish her testimony, after having broken down on the stand once already. After the trial concludes with the conviction of the murder suspect, they hug and Lindsay reels him in for a kiss but they are mobbed by reporters and miss their chance. They leave the courtroom hand-in-hand.
In the following episode, "Communication Breakdown," Danny spends a great deal of time throughout the episode picking out possible names for the baby, which he assumes will be a boy. When Stella posits that the baby could be a girl, Danny is skeptical, pointing out that his mother had only boys, and that Lindsay has three brothers. A text from Lindsay soon after proves Stella right; the baby is a girl. In "Greater Good" (episode 523), Lindsay, now back from Montana, goes into labor in the lab and has Adam take her to the hospital. Hawkes rushes Danny to the hospital to join his wife, who gives birth to a baby girl. Though they disagree initially on the baby's name (Danny wants to name the baby "Lucy," but Lindsay prefers "Lydia"), they do agree that they would like Mac to be the baby's godfather. Mac accepts. The following episode, "Grounds For Deception," reveals that Baby Messer's name is Lucy. Danny and Lindsay bring her to the lab, where their co-workers fuss over her. Danny becomes protective of Lucy when he sees that one of the co-workers is male and Lindsay says that Lucy "adores him."
In the episode after "Pay Up", "Epilogue", Danny is shot in the gunfire at the bar while protecting Lindsay and is in a wheelchair because he is paralyzed from the waist down. By the end of the episode he moves his foot slightly, showing that he is only temporarily paralyzed. Within a few episodes he is indeed walking again, albeit with the help of a cane. At the end of the episode "Dead Reckoning," the first thing he does onscreen without the wheelchair is hold his infant daughter in his arms.