The Old Bailey trial of Ian Huntley has heard how his girlfriend told police he was not a "violent person".
Ian Huntley is accused of murdering Jessica Chapman and Holly Wells
Maxine Carr said he was not involved in the deaths of 10-year-old Jessica Chapman and Holly Wells, but she could "not say 100%".
"He just wouldn't do it," Ms Carr said in her police statement, read out to court on Thursday.
Ms Carr denies helping an offender and conspiring to pervert the course of justice and Mr Huntley denies murder.
The pair's trial was hearing more evidence from police interviews with Ms Carr.
In them she denied being involved in grooming or murdering the girls or disposing of their bodies.
But she did admit that, after she gave a false alibi for Mr Huntley, he prepared a list of timings on a piece of paper because "he said I had to get the story right".
In one extract of the police interview with 26-year-old Ms Carr, a police officer put it to her that her then boyfriend could have killed the girls.
She replied: "He wouldn't hurt anybody, I know him inside out, he is a very emotional person."
Asked how she knew "100%" he was not involved, Ms Carr said: "I cannot say 100% - all I can say is I know Ian, I know Ian better than you or anybody here or anybody else or even his mother."
When told police had arrested Mr Huntley, and that his fingerprints were on the bag containing the girls' clothing, she began crying but continued to deny Mr Huntley had killed the girls.
She also denied the couple had any "sexual fantasy" involving the girls, or that the girls had been "groomed" for "a set plan".
Asked about their attitudes to child sex offenders or child killers, Ms Carr told police they both believed they should be shot or castrated.
In her police statement, Ms Carr said on the evening the girls disappeared - Sunday 4 August - Mr Huntley phoned her at her mother's house in Grimsby at about 1900 BST.
He mentioned two girls had been asking after her but did not mention the names of Holly and Jessica, who were last seen alive by a member of the public shortly after 1830.
She first heard that the girls were missing when Mr Huntley rang the following day at about 0900 and told her he had been helping police search for "some kids".
In a later phone call on Monday, she told police, Mr Huntley said to her: "'The bad thing about it is it's the girls that came and asked about you'".
Ms Carr said he then explained he had been outside their Soham home with their dog Sadie when the two girls appeared.
Mr Huntley was said to be 'very worried' as the search continued
"He just looked up and there were these girls and they asked 'How's Miss Carr?' and he was a bit gobsmacked because he didn't know who they were," Ms Carr said in her statement read out to the Old Bailey by a prosecution lawyer.
After a short conversation, according to Ms Carr, Mr Huntley said the two girls disappeared up the road.
The court heard that Mr Huntley was "rattled" when he knew he was the last person to see Jessica and Holly alive.
In the statement she repeatedly referred to how upset Mr Huntley was becoming, and said he told her: "They are going to arrest us both."
She told police: "I did not know what to say or anything ... he says just
tell them the truth, just tell them the truth about everything he said and
everything will be all right."
But, when a policeman making door-to-door inquires on 9 August came to her house, Ms Carr told him, falsely, that she had been in Soham on the day the girls disappeared.
She insisted, in her statement, that she would not have protected her then boyfriend from "the charges you are throwing at him, murder or abduction or whatever".
But she wanted to protect Mr Huntley from "the past", because of the nervous breakdown he suffered when he was previously falsely accused of rape.
And she insisted he did not make her lie - "I done it of my own accord to protect him".
Ms Carr denied being scared of Mr Huntley but said he had once slapped her across the cheek, which she said "shook me up".
Asked about her cleaning of the house - the prosecution allege the "ultimate spring
clean" was carried out after the girls went missing - Ms Carr told police she did it daily, and described herself as obsessive compulsive.
She said on her return from Grimsby she did various cleaning jobs - including the curtains and insides of the windows - as well as finishing off painting some tiles in the kitchen.
Also in the police interview, Ms Carr was handed a piece of paper with a list of times written on it: "4.55pm got in bath, 5.40-.5.45pm dog home, 6.15 girls arrive, 6.55 came down to put on tea."
Ms Carr admitted that Mr Huntley wrote the note because "he said I had to get the story right."
"So he wrote it down as he said if you're going to carry on lying like this you've got to get it right."
The case continues.