María LaGuerta

Season one

In the series' beginning, LaGuerta is depicted as a determined and ambitious woman with a stronger aptitude for political maneuvering than practical police duties. She holds a deep animosity towards Debra, Dexter Morgan's sister,^[2] but harbors an attraction to Dexter. In the conclusion of the first season, Captain Tom Matthews, her superior, removes her from her leadership position due to her inability to apprehend the Ice Truck Killer.^[3]

Season two

In the early episodes of season two, LaGuerta grapples with her demotion and dissatisfaction with her replacement, Esmee Pascal. To retaliate, she engages in a romantic relationship with Pascal's fiancé, Bertrand, which fuels Pascal's growing paranoia and instability. As Pascal's behavior becomes increasingly erratic, Captain Matthews is compelled to remove her from her position and reinstate LaGuerta.

LaGuerta implores Doakes to go along with Lundy’s investigation and discovers he is considering retiring from being an officer. She offers to set him up with another employer, and plans to meet him with Doakes that night. Doakes does not show up to the meeting.^[4] After Doakes becomes the primary suspect in the Bay Harbor Butcher case, LaGuerta endeavors to vindicate him. She receives information from a dubious source regarding two Special Forces missions undertaken by Doakes, which coincide with the deaths of two Butcher victims. In the season finale, Doakes and drug dealer Jose Garza are discovered dead in an apparent accidental explosion, leading to the case's closure. Despite the evidence LaGuerta uncovers, it is disregarded. Following Doakes' demise, LaGuerta appeals to police officers for contributions to his memorial fund, refusing to accept the notion that her deceased friend was a serial killer.^[5]

Season three

LaGuerta announces Batista’s promotion to sergeant, and she is reunited with Miguel Prado (Jimmy Smits) after his brother Oscar is killed. After Debra unintentionally badmouths Oscar in front of Miguel, LaGuerta convinces Batista to drop her from the case, and attends Oscar’s wake.^[6] LaGuerta tries to reassure Miguel that the police will find Freebo, though he is doubtful. After Batista and Quinn are offered information exonerating Chickey Hines, who Miguel convicted, LaGuerta confronts Miguel with the new evidence.^[7] At Batista’s mention, LaGuerta confronts Miguel over not speaking with Chickey Hines. LaGuerta gets frustrated when evidence suggests Freebo is probably gone.^[8] When LaGuerta again confronts Miguel over not talking to her witness, Miguel suggests that having to accept Doakes was the Bay Harbor Butcher may be clouding her judgement. LaGuerta gives a witness statement granting Hines an alibi to his attorney, Ellen Wolf.^[9] Ramon meets with LaGuerta after he begins working on the case of a woman murdered by the Skinner, and suspects him of using the case to insert himself into the investigation of his brother's death.^[10] LaGuerta is enraged at Wolf after finding out she is investigating Miguel for misconduct. Batista keeps her out of the loop while Debra looks into the possibility of Ramon as the Skinner, and LaGuerta compliments Debra after Ramon is arrested for false imprisonment.^[11]

LaGuerta gives Ramon a deal where he has to give up his shield and retire to not be charged, which mends her relationship with Miguel.^[12] LaGuerta asks Wolf to accompany her to a police charity and the two develop a friendship.^[13] After Wolf stops answering her phone, LaGuerta becomes worried and is horrified when her body is found at a cemetery.^[14] LaGuerta reports Toby Edwards as the suspect in Wolf’s murder, and interrogates him. She believes he is the killer until Quinn tells her of evidence that exonerates him. Miguel visits LaGuerta at her home, and the two kiss before being discovered by Miguel’s wife Sylvia (Valerie Cruz).^[15] Through her own personal investigation and input from Dexter, LaGuerta uncovers that Miguel is responsible for Wolf's death. LaGuerta confides in Dexter, considering him the only other person aware of the truth.^[16] After Miguel's demise at Dexter's hands, LaGuerta becomes distressed by the possibility of the Cuban community honoring Miguel by naming a highway after him. She desires to obtain solid evidence to prove Miguel's guilt in Wolf's murder. However, Dexter manages to persuade her that pursuing the case would only inflict further pain upon Miguel's family and the community, and even if successful, the evidence would be insufficient. Reluctantly, LaGuerta lets go of the matter.^[17]

Season four

In the beginning of season four, it is revealed that LaGuerta is involved in a romantic relationship with Detective Angel Batista. They choose to keep their relationship hidden from their colleagues at the homicide department, except for Dexter, whom both Batista and LaGuerta confide in. However, their situation becomes complicated when LaGuerta discloses their relationship to their superiors to prevent it from being used against them in a trial. As a consequence, they face the possibility of being reassigned, requiring one of them to leave the homicide department. Recognizing the significance of their jobs for their identities, Batista and LaGuerta decide to end their relationship and provide signed affidavits to confirm this. Despite their intentions, staying apart proves challenging, and they resume their secret encounters. To avoid potential consequences from higher authorities, they clandestinely marry, with Dexter serving as a witness.

Season five

LaGuerta arrives on the scene after Rita's murder and hands the case to the FBI, despite objections from Batista. She attends Rita's funeral, and admits to Batista that she was too frightened to handle the case, the latter consoling her.^[18] Batista discovers that LaGuerta has over $200,000 in a savings account, and tries getting advice from Quinn and Debra on how to handle the situation, to undesired results. Batista and Masuka go for drinks and a drunk Batista assaults a drunk police officer after he makes sexual remarks about LaGuerta ("she gave the best blowjobs in Miami").^[19] Batista is reluctant to tell LaGuerta what started the fight, and she demands specifics after Masuka brags about Batista’s conduct. Internal Affairs officer Jim McCourt (Raphael Sbarge) notifies her that Batista is being formally investigated after Lopez files charges and gets two witnesses to assert they saw Batista kick him while he was on the ground, charges that could get him incarcerated.^[20] LaGuerta orders Batista to visit Lopez and make amends with him. LaGuerta intercepts a conversation between McCourt and Batista, and tries getting McCourt to drop the case. Quinn gets arrested trying to get Trinity’s son to identify a sketch of Kyle Butler as Dexter, and LaGuerta puts Quinn on unpaid suspension and angrily scolds him for his theory.^[21] LaGuerta teams up with McCourt, and Batista begins to believe LaGuerta and McCourt are having an affair. He checks her cell phone for suspicious messages and later finds a rendezvous appointment in a hotel room. Outraged, he walks in on them, only to find out that it was intended to be a sting operation to apprehend a corrupt narcotics cop, in which LaGuerta agreed to participate to bail Batista out of the investigation.^[22] LaGuerta tries persuading Matthews to go along with the plan to stake out Club Mayan for the Fuentes brothers. She and Batista argue over her reasons for going to I.A.D. After Batista gets Yasmin Aragon (Jessica Camacho) to cooperate with the department in exchange for clearing her drug charges, Batista apologizes to LaGuerta, who admits she went to I.A.D to get his charges dropped.^[23]

LaGuerta and Batista speak with Jordan Chase after a car registered in his name is found with barrels containing dead women. At the stakeout, LaGuerta instructs Yasmin to sit with the Fuentes brothers so they can arrest them when they try leaving. Debra tries getting Manzon not to sit with the brothers, but LaGuerta overrules her. A shooting breaks out and Yasmin and Carlos Fuentes are killed. LaGuerta refuses to take responsibility for the incident.^[24] This incident further strains Batista's perception of LaGuerta. However, by the conclusion of the season, they had reconciled and mend their relationship.

Season six

LaGuerta and Batista go through a divorce after realizing their divergent desires. Following her blackmailing of Matthews with a contact list belonging to a madam, which includes his name, LaGuerta is promoted to the position of captain. Matthews assigns Debra as the new lieutenant, a decision that upsets LaGuerta, as she had promised the role to Batista. Initially uncertain, Debra seeks advice from LaGuerta, who intentionally provides her with unsound guidance in an attempt to undermine her. However, Debra gains confidence in her own abilities and becomes self-reliant. When evidence of Matthews' involvement with another prostitute emerges, LaGuerta initially instructs Debra to conceal it. However, LaGuerta warns Debra that she will face consequences if she deviates from the expected course of action.

Season seven

At the start of the season, LaGuerta discovers a blood slide containing the blood of serial killer Travis Marshall at the scene of his death. Recognizing similarities to the Bay Harbor butcher's methods, she begins an investigation to determine if the butcher is still alive and seeks to prove Doakes' innocence. Her suspicions turn toward Dexter when she learns about his boat's relocation during the Butcher investigation. LaGuerta seeks assistance from Matthews, who assures her that her suspicions are unfounded.

As LaGuerta and Matthews delve into the case, they revisit the cabin where Doakes died and uncover evidence linking Santos Jimenez to the deaths of Dexter and Brian Moser's mother. LaGuerta's suspicions of Dexter escalate after learning about his background and the disappearance of Jimenez. They search the area and discover evidence implicating Doakes, which LaGuerta believes was planted.

Eventually, LaGuerta devises a plan to confirm Dexter's identity as the butcher. She orchestrates the release of Hector Estrada, the man who ordered the killing of Dexter's mother, hoping that Dexter will target him. Dexter indeed tracks down Estrada but realizes LaGuerta's setup. Reluctantly, he releases Estrada to ensure his own escape, though LaGuerta deduces his intentions upon discovering the kill room.

LaGuerta has Dexter arrested for Estrada's murder, but forensic specialist Vince Masuka provides evidence that proves Dexter's innocence, leading to his release. Despite this setback, LaGuerta remains determined to apprehend Dexter, especially after finding circumstantial evidence linking him and Debra to the scene of Marshall's death. She confronts Debra with the evidence, but Debra defends herself.

As tensions escalate, Dexter concludes that the only solution is to kill LaGuerta. He abducts and kills Estrada, then renders LaGuerta unconscious upon her arrival. His plan is to stage the scene to make it appear as if LaGuerta and Estrada killed each other. However, Debra interrupts him and pleads for LaGuerta's life. LaGuerta implores Debra to kill Dexter, asserting her own moral superiority. Dexter relents and drops his weapon. Tearfully, Debra shoots a surprised LaGuerta in the chest, resulting in her death.^[25]