A lab worker accused of murdering a 23-year-old colleague during a brief relationship has claimed he acted out of "blind rage" after remembering sexual abuse from his childhood.
Ross McCullum, who admits strangling Megan Newborough and then cutting her throat, said his victim "could have been anyone" during an explosion of anger he said was "like a volcano".
A trial at Leicester Crown Court has heard McCullum, aged 30, admitted the manslaughter of Miss Newborough, but denies having murderous intent when he strangled her.
Prosecutors allege McCullum murdered Megan between 8.08pm and 8.49pm on Friday August 6 last year.He then used the human resources worker’s car to dump her body in a country lane near Woodhouse Eaves, Leicestershire.
Giving evidence in the fourth week of his trial, McCullum, of Windsor Close, Coalville, claimed he had made Miss Newborough a drink after she arrived at his family home.
He also said he had been to the garage, which had brought "personal information" into his mind and sent him into a "bit of a daze".
Answering questions from defence KC Kerim Fuad, McCullum said: "We went into the back room. We stayed there for about 15-20 minutes, just talking really.
"She (Megan) could see that something was up. I was just sweating and panicking. I should have said at that point, ‘I need to be on my own’.”
Asked what had then happened in the living room, McCullum said he and Miss Newborough were starting to engage in sexual activity, when he swore at her because he “felt a bit awkward”.
Claiming Miss Newborough, from Nuneaton in Warwickshire, had given him "a little bit of a slap" on the side of his leg in a playful way, McCullum told the jury: "She pulled me closer and said ‘come here’.
"That’s just when I exploded… just rage. I pushed her forward with all my strength. I have never ever felt like that before. It was like a volcano."
After being invited by Mr Fuad to explain at whom the “rage” was directed, the defendant answered: “I just pushed forward with everything I had.
“If I had not been in the garage… it wouldn’t have happened, it wouldn’t have ended up like that.”
Telling the court Megan had done nothing wrong, McCullum added: “I remember feeling like I couldn’t get out – she was trapping me. There wasn’t a thought process.
“It was just blind rage.”
Describing what he claimed was going through his mind, the former catering student told the court: “Fighting back, pushing back. It was like I was trying to get out.”
According to his account, McCullum paced around for five to ten minutes before seeing that Megan appeared to be dead.
“That’s when I saw the knife,” he told his trial. “It (cutting Megan’s neck) was something I just did, a rash impulsive thing. It just made things a million times worse. I don’t know why I did it.”
The court heard how McCullum, who had met Miss Newborough while working for brick-making firm Ibstock, searched the internet for pornography and Googled details of serial killers in the hours after disposing of her body.
Police also found that McCullum conducted online searches linked to serial killer Levi Bellfield, Soham killer Ian Huntley and Yorkshire ripper Peter Sutcliffe.
Asked why he had made the searches and sent messages to Miss Newborough’s phone despite knowing she was dead, McCullum said: “At the time I was being delusional. It was almost like a fantasy world.
“That wasn’t Ross. I am not perfect but the person who was doing that… sure it was me but it wasn’t rational me.
“I just cringe when I remember it and I hate what I have done.”
Among the internet searches was one for a category A prison, the court heard.
McCullum added: “I was just thinking where do these people go. I had literally just killed someone and I was panicking.
“I was worried about who I was going to be in (a cell) with.”
Claiming he had viewed internet pornography as a “safety blanket,” McCullum continued: “It takes you to that fantasy world where it wasn’t real. It makes you feel better for a short period of time.
“I was just drifting between what was and wasn’t real in my life. I had just killed someone… but at the same time I was still trying to be delusional.”
After telling police where Miss Newborough’s body was, McCullum, who claims to have a post-traumatic stress disorder, told the court he felt glad “the game was over”.
“I had to tell them what had happened,” he told the jury. “I felt like crap for what I had done. It was almost euphoric afterwards, after I had confessed.”
The jury has been told McCullum has never made a complaint to police about the alleged abuse, which he said involved a boy who he could not identify.
Mr Fuad told the jury at the start of the trial: "It is, put simply, the defence case that at the time he strangled her, he was suffering from post-traumatic stress disorder as a result of a series of acts upon him as a child.
"His case is that he did not have, nor could have, any reason, wish or any intention for Miss Newborough to be killed or to be the victim of any unlawful violence, but for the post traumatic stress disorder that consumed him at that time, in the sitting room."
McCullum denies murder. The trial continues.