The parents of a woman arrested over the murder of Meredith Kercher are to plead her innocence in a documentary to air next week.

Coulsdon university student Meredith was found dead with her throat cut in the room where she was staying in Perugia while she studied in the Italian city in November.

American student Amanda Knox, her Italian former boyfriend Raffaele Sollecito and Ivorian Rudy Hermann Guede have been held since November on suspicion of sexual assault and murder.

Knox, 20, Sollecito, 24, and Guede, 21, all deny involvement in her death and are yet to be charged with any crime.

Channel 4 says Sex, Lies and the Murder of Meredith Kercher will look at the case, including hearing from critics claiming the police were too hasty in their accusation.

Knox's parents explain to Cutting Edge why they think their daughter is innocent, and the heartbreak they experience every time they see her in prison.

Knox's mother, Edda Mellas, maintains her daughter's innocence: "She's absolutely innocent. There's no doubt in my mind. Never has been a shred of doubt in my mind that she's had nothing to do with this. Absolutely nothing."

The programme airs on Channel 4 on Thursday at 9pm.