Vincent Tabak turned from sordid voyeur to murderer after becoming obsessed with images of women being strangled during sex, it can be revealed today.

He also paid a prostitute having trawled escort and violent pornography websites in the weeks before throttling Joanna Yeates.

Detectives discovered his perversions had chilling parallels with how he killed his next-door neighbour.

Footage found on his laptops depicted women tied up in car boots - just as Miss Yeates's body was temporarily left after she died.

Three pictures also showed a blonde woman in a pink T-shirt and jeans closely resembling Miss Yeates on the night of her death.

Images seized by officers showed the woman with her top pulled up in a similar pose to how Tabak dumped Miss Yeates's body.

Tabak, 33, who never had a proper relationship until he met Tanja Morson online, was accused of misleading jurors by portraying himself as sexually inexperienced.

His depraved secrets were not heard by jurors trying him for murder.

But detectives privately believe he killed the 25-year-old in a bid to re-enact his violent perversions.

Tabak paid for sex with a call girl while on a business trip to Los Angeles less than two weeks before killing Miss Yeates, officers found.

He also contacted prostitutes in Newcastle last year - though it is not known if any transactions took place.

In the weeks after the murder, Tabak searched ''Jo Yeates'' on Google minutes before logging on to view several home-made sex videos.

On the morning of her death Tabak logged on to a pornographic website and while there was no evidence of a sex attack on Miss Yeates, police believe he was aroused and gaining sexual gratification from the killing.

Nigel Lickley QC, who made two failed applications to include the evidence in the prosecution case, told Bristol Crown Court how pornography depicting violence was found ''in a series of films''.

''We submit that these images explain why he held Miss Yeates by the neck,'' he told Mr Justice Field in the absence of the jury.

While in the US he made a series of calls from his work BlackBerry mobile phone to escorts called ''Princess Butter'', ''Rebecca Devine'', ''Michelle'' and ''Mimi''.

Having spoken to Mimi he made two cash withdrawals of 100 dollars each and booked into the cheap Peach Tree Inn at San Luis Obispo under the false name of Francis Tabak.

Mr Lickley told the judge: ''So in that instance there is direct contact, it would appear money withdrawn, followed by a further meeting and the overwhelming inference we would suggest in that instance, having done the research, made the contact, withdrawn the money, escort services were provided.''

He continued to trawl sex websites, including redtube and checked out live chat, strippers and escorts.

And two days later he booked into the cheap Peach Tree Inn at San Luis Obispo under the false name of Francis Tabak.

The next morning he checked out having paid the 43.81-dollar bill and returned to his own hotel, which his Bath-based employers Buro Happold provided.

Tabak, who had only left university in 2007 at 29 after 11 years of study, had also shown an interest in prostitutes during a business trip to Newcastle in May of last year, Mr Lickley said.

He logged on to the adultwork website and made several phone calls to escort agencies in the north east.

''At this stage there is a clearly an interest in escorts and telephone calls to numbers linked to that,'' Mr Lickley told the judge in the absence of the jury.

''The inference we seek to draw is that this determined activity and going as far as making telephone contact in Newcastle leads to the clear picture that the defendant was interested in escort services in so far as to make those calls.''

He also paid monthly subscriptions of £15 and £10 to access the Erotic Review and adultwork websites respectively, police discovered.

Images and videos depicting men gripping victims by the neck were found on a laptop and hard drives recovered from his home and office.

Films favoured by Tabak were entitled Sex and Submission, police searches of his computer equipment found.

Mr Lickley said: ''It is seen in the context of sexual activity that the women are degraded by the man.

''The defendant liked those films because he watched more than one and he watched some of them more than once individually.

''That suggests he derived sexual pleasure from them.''

The pictures of the blonde girl recovered from Tabak's laptop had a ''striking resemblance'' to Miss Yeates in terms of height, hair colour and what she was wearing, Mr Lickley said.

The murder fed Tabak's perversion for violent sex, police believe.

After Tabak spent Christmas with his girlfriend in Cambridge and New Year in Holland, detectives discovered that he had been googling Miss Yeates on his return.

On the morning of January 7, Tabak spent ''some time'' researching the investigation into the death of Miss Yeates, Mr Lickley said.

''From looking at the images of her he then moved to looking at images of pornography,'' the barrister added.

''He googled her name... less than two minutes later he started looking at the pornographic website redtube.com.

''Some of those films contained images of woman again being held by the throat.

''He received a text message from his girlfriend but continued watching the pornography.''

Mr Lickley sought permission to tell the jury about Tabak's secret life because he said the Dutchman had created a ''false impression''.

''Firstly, that he was sexually inexperienced, save for the relationship with Miss Morson,'' the barrister said.

''That he was in a monogamous, loving, caring relationship with her, characterised by a close mutual dependency.

''The defendant says that he misinterpreted, it would appear, what was said to him or done towards him or that Miss Yeates gave the impression that she wanted some sort of sexual encounter with him.

''In fact the defendant is sexually experienced beyond his relationship with Miss Morson in the sense that he has accessed websites allowing him to seek out women that he could pay, and we submit, did pay for sex.''