DS Naomi Cohen, portrayed by Ariana Fraval, first appears in episode 5269, broadcast on 3 October 2019. Fraval's casting was announced by her agent on 23 August 2019, while details about the character were announced on 3 October 2019. D.S. Cohen is introduced as a
detective sergeant who is investigating the murder of
Harry Thompson (
Parry Glasspool). Fraval stars opposite her husband, actor
Gregory Finnegan, who portrays Harry's boyfriend,
James Nightingale, and her first scenes on the soap were with him. D.S. Cohen arrives to take James Nightingale to identify the body of Harry Thompson. However, after Joel is threatened, he informs D.S. Cohen that a random person attacked him and it was not Liam. She later informs Diane about the release of Harry's body. D.S. Cohen questions Liam about the disappearance of Mercedes, but they are stopped when Mercedes' cousin,
Goldie McQueen (
Chelsee Healey), discovers her unconscious body in The Loft nightclub, having been shot. She then questions Liam about the lack of CCTV footage in The Loft during the shooting. During the following day, she collects alibis from Sylver, Liam and
Grace Black (
Tamara Wall). After receiving a tip-off from Liam, she searches
The Dog in the Pond public house for a gun, which Grace is able to hide. Sylver warns D.S. Cohen that Liam could have shot Mercedes, so when the police find the gun in Liam's car, she arrests him. She prepares to charge Liam for the shooting until James, his lawyer, intervenes and has the charges dropped. When blood is discovered at the shooting crime scene, Diane confesses to D.S. Cohen that it belongs to her. Diane also presents her with CCTV footage of her kissing
Edward Hutchinson (
Joe McGann) as her alibi, which also confirms the time of the shooting. After
Breda McQueen (
Moya Brady), who is a serial killer, anonymously hands in a written confession, D.S. Cohen runs forensics on the confession and assesses that Mercedes is the serial killer, so arrests her and clashes with Goldie. She then orders a search of Mercedes' home, but fails to find any evidence that could convict her. After a hostage situation at Breda's pig farm, where Breda is exposed as the serial killer (see
Hollyoaks Later (2020 special)), D.S. Cohen tries to ask Mercedes for her version of events, but she is rebuffed. Following the death of
Jesse Donovan (
Luke Jerdy), D.S. Cohen returns his personal items to his wife,
Courtney Campbell (Amy Conachan), and explains to his siblings, Grace and Liam, that Jesse died from
alcohol poisoning. After reviewing the footage of Jesse drinking, she decides not to launch an investigation into his death. D.S. Cohen later arrests
Mitchell Deveraux (Imran Adams) for
homophobic abuse against
Azim Desai (
Nav Sidhu), but releases him when Azim drops the charges.
Tony Hutchinson (
Nick Pickard), who was Breda's prisoner for months and is suffering with
post-traumatic stress disorder as a result, asks D.S. Cohen about Breda's body; she reveals that it was mostly burnt, fueling his paranoia that Breda has returned. After learning the whereabouts of
Warren Fox (
Jamie Lomas), who is wanted by the police, D.S. Cohen arrests him, but soon releases him when
Brody Hudson (
Adam Woodward) confirms Warren's version of events. She later arrests Warren after witnessing him assault Liam. Acting as Warren's lawyer, James confronts D.S. Cohen about the arrest and has him released. When
Felix Westwood (
Richard Blackwood) is attacked, D.S. Cohen questions his children, Mitchell,
Toby Faroe (Bobby Gordon) and
Celeste Faroe (Andrea Ali). Celeste lies that Mitchell was responsible for the attack, so D.S. Cohen arrests him. She then questions Mitchell and later, his boyfriend,
Scott Drinkwell (
Ross Adams). == Edward Hutchinson ==