|Portrayed by||William Gaminara|
|First Seen||The Fall Out|
|Last Seen|| Greater Love |
Awakening part 2 (flashback)
|Relatives|| Theresa Dalton (wife, deceased)
Cassie Dalton (daughter, deceased)
Janet Mander (former partner)
Leo was born in England in 1957. He lived in Sheffield before moving to London later in life. In college, Leo met a man named Sean Delaney, whom he remained good friends with for the rest of Sean's life. Leo trained as a forensic pathologist. At some point in his life, he met and married a school teacher named Theresa; in 1992, they had a daughter named Cassie together.
Silent Witness Edit
Leo moved down from Sheffield to take up a post alongside Sam Ryan in Series 6, first appearing in The Fall Out. On her departure he was promoted to head of department. In the Series 9 story Ghosts, Theresa and Cassie were killed in a tragic car accident, which left him heartbroken and continued to affect him for the rest of his life. Ever since, his motivation for work has become a search for justice. Leo believes that the course to justice isn't always as simple as following the rules and if needs be, he'll bend them occasionally. However, in Series 12 he showed a serious lapse of judgement after being stopped for drink driving.
Leo began a relationship with Professor Janet Mander in the Series 12, eventually moving in with her, but continued to struggle with his grief over his family's death. He eventually ended their relationship in the Series 15 story Redhill. In Trust Leo is infected with anthrax; fortunately, he is vaccinated before any permanent damage is caused. He was temporarily suspended from work after being set up by a government worker - who made it seem he'd taken sensitive case files home with him - to prevent him from uncovering a conspiracy in Legacy. Leo died in the Series 16 finale Greater Love, when he sacrificed himself to save many others - including his team - from a terrorist bomb explosion in Afghanistan. He is buried in England, alongside his wife and daughter. He is succeeded in his role as head of the Lyell Centre by Thomas Chamberlain.
He briefly appears in a flashback in part two of Awakening.
The team leader, Leo is a highly experienced pathologist and born teacher who upholds the standards of his team at the Lyell Centre and leads them with a wisdom that only years of experience can bring him. Not one to mince his words, he is tough and unafraid of delivering difficult truths, but he also has an understanding of how people operate. Leo is not usually an aggressive person, though in times of emotional stress he can become so - in Redhill, he punches a corrupt prison guard when he threatens Janet. Leo often took a strong opinion on cases and frequently became emotionally involved.
Leo was initially somewhat antagonistic towards Harry, with the two becoming overly competitive after Sam Ryan left. Eventually, though, they warmed up to each other and became good friends. Leo was shown to be upset, but accepting when Harry decided to leave and stated he couldn't help but compare other candidates to Harry, showing he admired the man.
Leo had a paternalistic relationship with Nikki, with him stating at one point that he cared for Nikki and Harry as deeply as his family. Leo respected Nikki, though her impetuousness sometimes exasperated him. Leo sacrificed himself trying to protect Nikki, among others, citing her as being one of the things he truly loved.
Leo likes Jack almost from the moment they meet, admiring his skills as a forensic scientist. He was one of the only people who seemed to be able to talk Jack around if his temper got the better of him and sacrificed himself to save him and numerous others.
Janet Mander Edit
Leo and Janet were involved in a romantic relationship. Leo appeared to care deeply for Janet and respected her work as a profiler, but was reluctant to begin a family with her, only agreeing to adopt a child with her to make her happy. He later confessed that he never wanted to adopt. It became clear by Series 15 that Janet loved Leo more than he loved her, with Leo spending more and more time away from home and even avoiding talking about her - presumably out of guilt. He eventually admitted he no longer loved her. In spite of this, he still cares for her, as in the same episode he rushes to save her when he believes she is in danger from Daniel Kessler.
- Leo Dalton has appeared in the second highest number of episodes out of all the main characters, having appeared in a total of 107 episodes (including his flashback scene in Awakening).
- Leo's gravestone reveals he was born in 1957, thus making him fifty-six years old at the time of his death.
- Leo is similar to his successor Thomas Chamberlain, in that they were both married with a daughter. However, Thomas' wife leaves him and his daughter in in primary school, whilst Leo was happily married with a teenage daughter before their untimely deaths.