DCI Jill Marsden is a fictional character in the BBC soap opera EastEnders, played by Sophie Stanton. She made her first appearance on 5 March 2001 investigating the shooting of Phil Mitchell (Steve McFadden), which was part of the whodunit storyline "Who Shot Phil?". Marsden returned in 2002, 2003 and 2009 (for another whodunit storyline, "Who Killed Archie?"). She returned on 5 January 2012 for her third whodunit storyline, "Who's Stalking Phil?", departing four months later on 10 May 2012. Marsden returned for two episodes on 17 August 2012 to conclude the latter storyline. On 16 July 2015, she returned for part of the "Who Killed Lucy Beale?" whodunit storyline.
When she was brought back in 2009, Marsden's feelings were explored in a segment of the BBC EastEnders homepage entitled "Marsden's Video Diaries", documenting the character's thoughts about the storyline in which she was involved. Marsden's relationship with Phil has been explored since her first appearance, with the BBC describing their relationship as a "romance in negative...her ultimate dream is that some day she'll get [Phil] behind bars" and the Daily Mirror Tony Stewart calling her Phil's "arch enemy".
The character has been criticised by police detectives who felt that Marsden's habit of discussing investigation details with suspects (as her colleagues accepted bribes) did not properly represent their profession. In response, the BBC said it had sought advice from a police consultant for storylines involving Marsden.
Storylines
2001–2003
Jill Marsden first appears on Albert Square in March 2001, having been assigned as the chief police detective in charge of investigating the shooting of local hardman Phil Mitchell (Steve McFadden). She identifies the five main suspects: Phil's stepson Ian Beale (Adam Woodyatt), ex-business partner Dan Sullivan (Craig Fairbrass), sworn enemy Steve Owen (Martin Kemp), love rival Mark Fowler (Todd Carty), and former girlfriend Lisa Shaw (Lucy Benjamin). After Marsden interrogates each of the suspects behind Phil's shooting, it is eventually transpired in April 2001 that Lisa was the culprit. However, Phil gradually forgives Lisa and decides to frame Dan for the crime instead. He plants the gun, which Lisa took from Steve's office, in Dan's possession and enables for Marsden and her colleagues to arrest Dan for shooting Phil. A couple of months later, however, Dan is acquitted due to lack of evidence. Marsden later arrests local housewife Little Mo Slater (Kacey Ainsworth) for the attempted murder of her husband Trevor Morgan (Alex Ferns). Little Mo claims self-defence, since she has been a victim of domestic violence at the hands of Trevor. The trial ends, with Trevor's treatment of Little Mo revealed. In 2003, local resident Sonia Jackson (Natalie Cassidy) visits Marsden with evidence that Phil killed his ex-girlfriend Lisa. Marsden sets up a honey-trap for Phil in order to obtain a confession from him, with PC Kate Morton (Jill Halfpenny) and DI Dominic Price (Paul Brennen) aiding her in the case; however, this fails when Kate falls in love with Phil and Marsden fires her. Marsden arrests Phil, but with insufficient evidence and no confession he is released. It later emerges that Lisa is safe and well, and Phil is innocent. This forces Marsden to let Phil off the hook, but she later arrests him for armed robbery; Phil's arch-rivals Den Watts (Leslie Grantham) and his illegitimate son Dennis Rickman (Nigel Harman) have worked together to set him up for the crime in revenge for what he did to their beloved family member, Sharon (Letitia Dean).