It can be inferred that Danny grew up on Staten Island, in a family under surveillance (as hinted at in the episode "Tanglewood"). As a result, he formed his own set of hybrid ethics, caught between the world of lawbreakers and law enforcers. Though very little is known about the Messer family, Danny openly admits that he has had a very rocky relationship with his older brother, Louie, since a fateful night in 1991. After promising to take Danny to Atlantic City with some of his friends, they 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 sent Danny away to prevent any involvement in the subsequent murder of that drug dealer (episode 220, "Run Silent, Run Deep"). Despite the strained relationship that resulted, Danny would later come to lend money to Louie on more than one occasion (episode 211, "Trapped").
While 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 graduating first in his class at the NYPD Police Academy, (episode 122, "The Closer"), Danny was chosen by CSI team leader Mac Taylor to join his team, an honor and a responsibility that he attempts to live up to each day.
In The Party's Over, Danny tells Stella that he comes from a family of cops.
Outside the Lab:
It has been implied that Danny is in his early 30s; Lindsay Monroe made a reference to his 30th birthday (episode 208, "Bad Beat"). Danny attended college and played minor league baseball until his wrist was broken during a baseball game that he was playing in. He took a ball in the head, and before he had a chance to do the same to the pitcher, the benches were cleared and he got caught up in the pile-up, shattering his wrist and ending any hopes for a career as a baseball player (episode 509, "The Box"). He is a very good handball player, once using his skills to acquire evidence (episode 216, "Cool Hunter"). He grew up in the same neighborhood as the Tanglewood boys, but maintains he was never a part of the gang like his brother, Louie, was (episode 220, "Run Silent, Run Deep").
On the Job:
On the show, Danny has displayed a tendency to follow his intuition when solving a case, rather than relying on the evidence, for which Mac has reprimanded him (episode 105, "A Man a Mile"). He was also once reprimanded for working to solve a case even after being ordered by Mac to move on to another one due to the victim having died a natural death (episode 119, "Crime & Misdemeanor"). Danny is a very suspicious person; though he gets along well with the rest of the CSI team, Detective Don Flack is one of the few people he truly confides in.
Danny is given control of his first crime scene in season 1, episode 6 "Outside Man". Mac tells him and Aiden that the crime scene at a robbery homicide is theirs, that Danny's in charge. The end of the episode says that Danny is on a promotion grid.
Almost a year after a episode featuring a case that involved the Tanglewood Boys gang (episode 114, "Tanglewood"), Danny was implicated in a 15-year-old cold murder case. Louie is severely beaten by the gang and left in a coma after attempting to prove Danny's innocence. With Mac's help, Danny eventually clears his name, thanks to a taped confession from the real killer (episode 220, "Run Silent, Run Deep"). Louie's condition is still unknown, though it is widely presumed that he is still comatose.
It seems that Danny is particularly sensitive when it comes to suspects who act out on the loss of a loved one. In episode 304, "Hung Out To Dry," Danny tells murder suspect Shane Casey that he understands Shane's desire to clear his brother Ian's name, but does not agree with Shane's methods. Danny's words come back to haunt him later when, during the events of "Raising Shane" (episode 311), Shane tries to exploit Danny's sympathy for his situation, as well as Danny's concern for Louie, to get Danny at gunpoint to process the since-abandoned crime scene to obtain evidence that would prove Ian's innocence. To Shane's despair, the CSI brings evidence with him that proves Ian's guilt, and the police take Shane into custody without incident.
In the episode "On The Job" (episode 121), Danny's relationship with Mac becomes strained when, during a critical case, Danny fires his weapon blindly in a shootout that resulted in the death of a police officer. Ultimately, it is determined that someone else actually fired the fatal shot. Nevertheless, Danny is taken off the promotional grid after talking to Internal Affairs when Mac specifically told to him wait until the preliminary evidence report was in. The mistrust fades by the end of Season 2, when Mac talks to him outside the hospital after the events that leave Danny's brother Louie comatose (episode 220, "Run Silent, Run Deep"). Danny is annoyed when he discovers he is evidently the last to learn about the romantic relationship between Mac and Medical Examiner Peyton Driscoll, especially that "even Flack" knew about it before he did (episode 316, "Heart of Glass").
Danny takes it upon himself to trade shifts with Lindsay Monroe in episode 324, "Snow Day," taking her place to assist lab tech Adam Ross at a warehouse crime scene. When he arrives, he is taken hostage and held along with Adam by Irish mobsters who hope to use the situation to distract the NYPD while others of their clan break into the lab to retrieve a huge cocaine seizure from earlier in the day. Danny is badly beaten during his captivity (taking a total of 4 blows to the head, one to the spine and having his left hand broken), but with Adam's help, manages to take down their captors in time to be rescued by the officers gathered outside.
In The Party's Over, Danny backs out of a crime scene, claiming to be sick, and goes on a strike of sorts, or blue flu, due to pay issues within the NYPD and the crime lab. When Stella Bonasera arrives at his apartment to confront him, she reluctantly agrees that she sees where he's coming from. He also earns the ire of Hawkes, who refers to him as "selfish". At the end of the episode, things seem to be forgiven between the two.
Relationships:
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."
Aiden Burn:
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 Lily, the first officer on the scene. After putting an abrupt stop to their flirtation, they return to work and later he teases her, indicating his possible jealousy. 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, content that they have fulfilled a promise to put Pratt behind bars for his crimes.
Lindsay Monroe:
Danny initially indulges in some friendly hazing of Lindsay Monroe, the detective brought in from Bozeman, Montana, at Mac's request to fill the gap in the roster 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 few episodes they are both stand-offish in their interactions. Soon though, they 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 feelings towards Lindsay manifest themselves in his objection to her volunteering to go undercover, and his holding her close to him after the team rescues her. In the following episode, "Love Run Cold," he unsuccessfully tries to continue their relationship, but Lindsay stands him up for a date and refuses his efforts to offer her support. 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 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 third season finale episode 324 "Snow Day," Danny and Lindsay sleep together on the billiard table at Danny's after an evening of drinking and playing pool at Danny's apartment.
Danny and Lindsay's romantic relationship is not featured in the early episodes of season 4, although there are several scenes of them bantering. In episode 401 "Can You Hear Me Now?" Lindsay slips a can of condom spray into Danny's shirt pocket while giving him a suggestive look.
Things take a downward turn in Danny's life in episode 411 "Child's Play," when a neighbor's child, Ruben Sandoval, whose care had been entrusted to Danny for the day, is killed by a stray bullet during a bodega robbery. Danny's grief and guilt plague him over the next several episodes, causing him to withdraw from Lindsay and act to protect the boy's mother, Rikki Sandoval. In episode 413, "All in the Family," Lindsay covers for Danny when he skips work to search for Rikki, who has stolen Danny's service revolver and gone to hunt down and kill the man she blames for her son's death. Flack and Danny intervene before she fulfills her plan. While Flack argues that Danny needs to report what happened, Danny is reluctant to cause trouble for Rikki, who is nearly crazed with grief. At the end of the episode, Rikki chooses to turn herself in to the police. In episode 416, "Right Next Door," Danny and Rikki are shown indulging in an affair. When Lindsay calls him, Danny blows her off as he is making breakfast for Rikki. Later on, when Lindsay is standoffish towards him, he thinks that she is still moping over his forgetting her birthday, but she eventually lays her feelings bare, vowing that even though she had fallen in love with him, she would figure out how to fall out of love with him.
In the next episode (episode 417, "Like Water for Murder"), however, Danny is again flirting with Lindsay in the lab. He upsets her when he suggests they get together to watch a movie, causing her to leave the lab abruptly. In episode 419 "Personal Foul," Danny calls Lindsay, admitting that he has missed her and asks her to come see him at his apartment. Not long after, Rikki Sandoval tells Danny that she is moving away, and both acknowledge that their fling had been a mistake.
Anna Belknap's real-life pregnancy inspired the storyline in which Danny learns that Lindsay is pregnant with his child. This was announced in the 9th episode of the 5th season, "The Box." [1]. In "The Box," much of the episode is shown from Danny's point of view and details his reaction to Lindsay's admission of her pregnancy and her remarks that she "knows him" and does not expect anything from him. Though he is scared of the changes that Lindsay's pregnancy will bring, by the end of the episode, he makes the decision to stand by Lindsay, figuratively (and literally, in context).
In episode 510, "The Triangle," Danny expresses concern over the baby's health and asks Lindsay to marry him. To his surprise and disappointment, she declines. Later, after the case has wrapped up, he presses her about her unwillingness to marry him. She explains that she merely feels that it is the wrong time and that she wants to get married for the right reasons. Seemingly satisfied with her answer, Danny then tells Lindsay that he loves her, which she reciprocates. They then go see Mac together to break the news of the pregnancy to him.
Subsequent episodes show Danny eagerly anticipating becoming a father; he puts his hand on Lindsay's belly when she says that they baby kicked ("Forbidden Fruit") and he sits at eye level with her belly as he reads from a comic book. When he is interrupted by the results of his DNA evidence, he kisses Lindsay's stomach and promises the baby that he will be back.
In episode 517, "Green Piece" Danny expresses concern when Lindsay offers to help at a crime scene. and they talk about her upcoming trip to Montana to see her family. Later on, Danny talks with Mac about Lindsay. At the end of the episode, Danny takes Lindsay, who is protesting that she needs to pack for her trip the next day, to city hall. Under the pretense of meeting some friends, he brings her to the city clerk's office. He reiterates his feelings for her and asks again Lindsay to marry him. This time, Lindsay agrees. The friends turn out to be Mac and Stella, who witness Danny and Lindsay's wedding. The vows are read as a montage of the couple's history, from their first meeting in Season 2's "Zoo York" to "Forbidden Fruit", is shown.
In "Point of No Return" (episode 518), Danny is forced to kill a crime scene suspect in self-defense. After he returns to the lab, he begins to understand the gravity of his new life; he looks in the mirror and realizes that he came close to getting killed himself, which would have widowed Lindsay and left their baby without a father.
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 and grandmother had only boys. A text from Lindsay soon after backs Stella up; 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."
Family:
Wife: Lindsay Monroe
Brother: Louie Messer
Daughter: Lucy Messer
