This entry contains spoilers for all aired UK episodes and so should be avoided if you are a fan of the show from outside the UK.
DSI (Detective Superintendent) Peter Boyd
A textbook example of Rabid Cop, Boyd is just as passionate as he is ruthless in his pursuit of justice. His willingness to bend or outright break rules and tendency to get angry with and harass the people he interrogates has often brought him trouble. That said, he has a tendency to get angry with pretty much everyone.
Boyd is also somewhat of a Deadpan Snarker, once involved three suspects in a Pub Quiz parody and was also arrested for drink driving. Has a weakness for pretty women.
His son, Luke, missing since the early 1990s, returned in Season 7, but ultimately committed suicide by drugs overdose. The precise impact on Boyd is as yet unclear. It was revealed in Season 8 that the "suicide" was murder, which led to a dramatic cliffhanger as Boyd was given the option to exact revenge. He and Grace are known to bicker Like an Old Married Couple.
Dr. Grace Foley
A Forensic Profiler with 30 years experience, Foley is mother to the team and tends to be used in a "tea and sympathy" role. She also had a brief bout with stomach cancer and she had to leave the unit briefly for the operation. She also became pregnant years ago when falling in love with the head of her first murder case. Saying it didn't end well would be an understatement considering she only found out he was married after she got pregnant, and then he died in a car crash while drunk at the wheel, while Grace miscarried. The loss of her unborn child continues to haunt her.
Took over from Felix. Eve, The Coroner, was involved in mass grave excavation in the aftermath of the Balkan Wars. She had her own Spin-Off called "The Body Farm" after the end of Waking The Dead. However, It only ran for one series due to poor ratings.
An original member of the team. She was The Coroner who was unafraid to speak her mind, usually with Boyd. She brought humor to the team and was good friends with Mel, knowing her before joining the team. After Mel died Frankie was traumatised and chose to leave the unit, returning to research. She was replaced by Felix Gibson in season 5.
DC Amelia "Mel" Silver
Mel was a feisty young achiever who worked hard to be promoted. She was also best-friends with Frankie. She was adopted as a child and tried to get into contact with her biological mother, but couldnt reveal her true identity as her mother had a new family. She was killed in the fourth season finale after being thrown off a roof and landing on the windscreen of the car Boyd and Grace were driving. Her shocking death shook the team to the core and it took Boyd over two series to come to terms with it. Her Jewish background would prove relevant in the later "Yahrzeit" episode, when an item of jewellery was sent to her last workplace. She'd been working on a case going back to WW2 with an American Mossad agent.
DI Spencer "Spence" Jordan
Frequently involved in Good Cop/Bad Cop stuff with Boyd as the Bad Cop.
He finds out in Season 3 that his father is alive, despite thinking he was dead since he was a child.
At the end of Season 5, he was shot in a CliffHanger ending, but emerged to have fully recovered in Season 6, getting a tattoo around the scar.In Season 8 he transfers out of the unit to CID but still liases with them for "Endgame". In Season 9 he has transferred back into the unit.
DS Stella Goodman
Born in the UK to an French mother and English father, her police officer father was killed and she moved to France, spending most of her childhood there.
Entering the Cold Case Squad after Mel Silver's death, she was unwittingly spying on them for her godfather. However, her loyalty is now unquestioned.
Bi-lingual in French and English, Goodman is acknowledged to be the most attractive member of the team by most sources and usually has dyed red hair, but this is not always the case. However, she remains single, although her ownership of a cat is not confirmed one way or the other.
She is a qualified firearms officer.
Stella has been used in a Rabid Cop role, in one case threatening an Algerian suspect with nastiness and claiming she had a relative paralysed in a terrorist attack. Boyd congratulated her on a successful deception- she inferred it that possibly wasn't. She was shot by a suspect and died in the first episode of the eight series.
DSI (Detective Superintendent) Sarah Cavendish
Irish born Sarah was a Broken Bird transferred to the unit at the beginning of series nine to replace Katarina Howard. She was moved from Counter-Terroism after an operation she was leading went wrong which led her to become the Scape Goat. Boyd had no say in her transfer. Her Dark and Troubled Past caused problems during cases including her Drowning Her Sorrows. Sarah learned to play by the rules which often put her at odds with Boyd`s way of getting results and resulted in her reporting him and causing his sacking. In a desperate state she tries to make amends and spies on a suspect, discovering his crimes, which leads to her being strangled and her body planted in Boyd`s shed in an attempt to frame him.
Sarah was one of the youngest Superintendents in the history of the Met having received this level by her early-thirties and a high flyer until the incident.
DS Katrina Howard
Howard appears in the beginning of Season 8, where she helps the team in solving a case. She has a history of insubordination. After Stella dies Katrina is transferred into the team as her replacement, at Boyds request. She doesnt have a major role within the team though, and she doesnt return for Season 9 and isnt even mentioned again. She is replaced by Sarah Cavendish.
Felix was the pathologist that replaced Frankie for Season 5. By Season 5 she had already been with the team for some time. Felix didnt have the humour that Frankie had but gave the information to the team in a more insightful way. She would regularly gather evidence at crime scenes. In the finale of Season 5 she discovers Stella is the mole on the team but is injured by a gas bomb meant for Spence. She makes a full recovery but doesnt return for Season 5 and her departure is never explained.