A schoolgirl who posed as a boy call Scott for three-and-a-half years to get another female into bed has been jailed for three years.

Justine McNally, 18, duped the 16-year-old into believing she was boy as they dated online – and carried on tricking her after they met.

Glaswegian McNally, then 17, lured the London schoolgirl into three sex sessions, promising they would get married and have children.

The girl was even fooled into thinking she had lost her virginity to McNally in a darkened bedroom of a family friend’s house.

McNally’s secret was only exposed when the girl’s mother found a strap-on dildo in her backpack.

‘Because of the abuse of trust, the trauma to the victim, and the peculiar circumstances, this is an extraordinary case’, said prosecutor David Markham.

‘This case is about the defendant, then aged 17, sexually assaulting the victim, then aged 16, by deceiving her into believing that she, the defendant, was a boy.

‘She obtained consent to physical intimacy between them by fraud. The case involves a very serious abuse of trust.’

McNally and her victim started their relationship when aged 12 and 13 after meeting through an online videogame.

During their three-and-a-half year online relationship, the girls ‘spoke about what they wanted to do to each other’, said Mr Markham.

‘Scott spoke about what he wanted to do with his d*ck.’

They eventually met in March 2011, when McNally, posing as a Goth boy called Scott, came to visit the girl in north London, staying with a friend of her family.

They had talked about having sex during online webchats on MSN and on video calls, and the relationship turned physical on the first visit.

But McNally refused to remove her clothes while sexually touching the girl, the court was told.

‘(The victim) offered to perform oral sex on him and went to touch his penis, but Scott said he didn’t want her to do that and he was happy to pleasure her’, said Mr Markham.

‘So she did not touch his penis at any point.’

He said at the first of three encounters, in March, May, and August 2011, the two girls tried to have sex.

‘She (the victim) believed intercourse was being attempted, Scott had said he wanted her to lose her virginity to him and she was trying to make him happy’, said Mr Markham.

‘But she suffered a lot of pain and they settled for cuddling up together.’

The girls broke off their individual relationships and believed they were girlfriend and boyfriend, making plans to start a life together, the court heard.

‘They talked about getting married and having children in the future’, said Mr Markham.

‘Scott described himself as having an unhappy home life in Glasgow from which he wanted to get away.’

When McNally tried to break off a previous relationship with a girlfriend in Glasgow, her cover was nearly blown when the victim and the girlfriend got into a furious row.

‘That girlfriend made a comment about Scott being a girl’, said Mr Markham.

‘When this was put to the defendant, the defendant laughed it off and joked about it. The way Scott dismissed it reassured her that everything was fine.

McNally’s secret was finally exposed in November 2011, when the family friend she was staying with got suspicious and looked through her possessions while on the phone to the girl’s mother.

‘The friend found a bra, a size 12 River Island top, and as she was talking, she found a strap on penis in the bag’, said Mr Markham.

Later in the evening, after dropping McNally off at the friend’s house near Tottenham Hale train station, the mother said to her daughter: ‘You do know Scott is a actually a girl?’

‘The victim entered a state of shock and denial, didn’t know what to think or what to do’, said Mr Markham.

The mother and daughter then confronted McNally, who produced a picture on Facebook of her dressed in pink clothing and heels, and said she wanted to have a sex change to continue the relationship.

Mr Markham said the victim was ‘literally sickened’ by the revelations, and eventually ended the relationship and called police.

She told the court she now struggles to build relationships with friends and boyfriends, preferring to isolate herself.

‘The sense of violation and vulnerability engendered by this crime left her with feelings of confusion and bewilderment’, said Mr Markham.

‘What should be an exciting era in her life has been darkened by what has been done to her.

‘She feels completely bereft and besieged with self-doubt.’

The court was told McNally had a difficult upbringing, with her parents getting divorces.

Keith Thomas, defending, asked for McNally to be spared jail so should could be treated for her gender issues.

McNally, of Cambuslang, Glasgow, admitted six counts of sexual assault by penetration, contrary to the Sexual Offences Act 2003.

The teenager was tearful through as the sentencing hearing as she was told prison was the only option for her crime because of the damage to the victim.

‘She had her first sexual experience with you, and you abused her trust so badly she finds it difficult to trust other people’, said Judge Patrick.

‘I was selfish and callous behaviour – a grave abuse of trust of her, her family and friends through your behaviour over a period of years.’

The judge said her disguise as a Goth called Scott fooled everybody when she came to visit the girl in London, making trips to Camden and a fireworks night in Enfield.

‘They met you with good faith and welcomed you into their homes’, he said.

The court heard the girl had gone out to buy condoms ahead of sex sessions with ‘Scott’, and fully anticipated they would have sexual contact.

‘You put your feelings before those of anyone else’, said Judge Patrick.

‘You have had a troubled history, but without wishing to minimise the effect of that on you, it’s no more remarkable.

‘You found the process of puberty complicated and had problems coming to terms with your sexuality.’

Judge Patrick said she would spend half her three year prison sentence behind bars before being released on licence.

‘Clearly you didn’t appreciate the seriousness of what you were doing’, he added.

‘You are an upset, distressed you woman, but the offence is so serious that a custodial sentence must follow.’

McNally, supported by her father in court, will be on the Sex Offenders’ Register for life and is banned from contact the victim or her mother.

He passed concurrent three year sentences for each count McNally had admitted.

The first count will lie on file.