STUART Hazell murdered Tia Sharp in a "sudden and violent attack" and then took a photograph of her "posed" body, a court has heard.
Jurors at the Old Bailey were told the 37-year-old had a "sexual attraction to young girls, particularly Tia".
Photographs and movies of the 12-year-old sleeping were found on two memory cards hidden in the house he shared with her grandmother, the court was told.
Hazell, who denies murder, is expected to argue that he "panicked and didn't know what to do" after Tia accidentally fell down the stairs and broke her neck.
Jurors heard how her body was carefully wrapped in a sheet and bin bags before the "parcel" was sealed with sticky tape and placed in the loft of the house in The Lindens, New Addington.
It took police two separate searches of the loft before they found the body on August 10 last year.
Andrew Edis QC, prosecuting, said: "They only found it because it had started to smell. As you can imagine, a week in a hot loft in August would have that effect.
"There was a parcel containing the body which had been carefully wrapped – in a sheet first and then bin bags separately – in order to try and seal it using Sellotape.
"As you can imagine that's not a particularly easy thing to do with a dead human being. But that's what had been done, no doubt to prevent any leakage.
"It was done for a purpose, a reason – something you may want to think about when you are talking about the panic."
Tia Sharp was last seen alive while making her way to her grandmother Christine Sharp's house on August 3. Hazell, an unemployed painter and decorator, was Ms Sharp's boyfriend and lived at the address.
Mr Edis told the court how Hazell had been secretly filming Tia when she stayed over and had a sexual interest in young girls.
On one of the memory cards police found were indecent images of children, bestiality and photographs of young teenage girls wearing glasses while performing sexual acts.
There were also images taken from a website which, the court was told, was regularly visited by paedophiles.
The court also heard that Hazell had used his phone to search for "naked little girlies" and "under-age photos" on the internet.
The prosecution believe he murdered Tia in the early hours of August 3.
The Raynes Park High School pupil regularly contacted a friend using BlackBerry Messenger (BBM). The last message she sent was at 12.48am that morning.
Jurors were shown an extremely distressing photograph of Tia, found on one of the memory cards, which the prosecution alleges was taken at around 6am that morning.
Pathologist Ashley Fegan-Earl examined the picture and said it was highly likely it had been taken after she had died.
Mr Edis said Hazell had "posed" the schoolgirl for his own sexual gratification.
His semen was found on a duvet cover and pillowcase recovered from Tia's room as well as her pyjamas and a pair of her floral boxer shorts.
Tia's blood was found on the bed covers and on a sex toy recovered from the house by police.
Dr Fegan-Earl was unable to establish a cause of death, but found she had suffered no broken neck of fractured skill.
His findings were consistent with suffocation, the court was told.
Tia's family, including her mother Natalie Sharp, wept as the details of the case were read out.
Hazell, wearing black glasses, tracksuit bottoms and a faded black t-shirt, looked on impassively.
After Tia was reported missing, Hazell told the police she had left home in the morning – without her phone - to go shopping at the Whitgift Centre.
Tia's apparent disappearance prompted a massive missing persons hunt which involved more than 80 police officers.
The court was told that Hazell had planned to remove the body from the house but was foiled because the area was "besieged by the media".
Mr Edis said: "That was to be a terrible nuisance to Mr Hazell. Normally he has the run of the house in the hours of darkness, quite often when Christine is at work.
"No doubt when he put her in the loft, having wrapped her up as he had done, he expected there would be an opportunity for him to go back to the loft and take her somewhere else.
"But of course that wasn't possible with all the local people, the press and the police laying siege to the house."
While her body was in the loft he gave a television interview to ITN in which he reacted angrily to the suggestion he had hurt Tia, telling the reporter he looked upon her like his own daughter.
On August 10 a police conducted a third search of the house after an officer noticed the smell. Tia's body was found in a loft alongside a second bin bag containing items of clothing, including damaged glasses, jeans, a pair of trainers and an Umbro top.
After being arrested in Merton later that day, Hazell chose not to comment during a police interview.
Later he told officers at Belmarsh prison "it wasn't a sexual thing" and that he "wasn't a nonce".
He added that Tia had fallen down the stairs and broken her neck, said Mr Edis.
"He then took Tia upstairs to bed thinking she would 'get better'," he added. Hazell then says he panicked and put her body in the loft covered in a blanket.
The trial continues.
