The Murder of Becky Watts is examined in new ITV documentary The Murder Of Becky Watts: Police Tapes.
In this new documentary tonight at 9PM on ITV, Susanna Reid gains unprecedented access to never seen before police tapes from the investigation into the murder of Becky Watts, revealing the inner workings of the case and the strategies detectives used to snare her killers.
But who killed Becky Watts and what happened to her killer?
Becky Watts was 16 when she went missing in an "out of character" disappearance in February, 2015.
A week later, two people were arrested on suspicion of kidnap and later murder, when body parts were discovered in a house in Bristol. The police eventually arrested a further five people on suspicion of assisting an offender.
The prime suspects turned out to be Becky's step-brother and his girlfriend, Nathan Matthews and Shauna Hoare, who were both charged with murder and other crimes.
In court, Nathan admitted killing Becky but claimed the death was an accident while Shauna denied any involvement in the teenager's death.
At the end of the trial, Nathan was found guilty of murdering Becky wile Shauna was found guilty of manslaughter.
Both were also convicted of a range of other crimes related to the attack, including conspiracy to kidnap, perverting the course of justice, preventing a lawful burial by dismembering and hiding her body, and possession of two stun guns.
Nathan was given a minimum off 33 years in prison while Shauna was sent away for 17 years. The pair later failed to appeal the convictions.
Two others were given sentences of two years and 16 months for assisting an offender.
In concluding the case, the judge said: "Finally I should like to pay public tribute to the family of Becky for the dignified way in which they have conducted themselves throughout these proceedings... Hearing the evidence during the trial has been difficult for anyone but it is plain that it has been an immense burden for the family."
The Murder Of Becky Watts: Police Tapes airs at 10PM tonight on ITV.