After the jury gave their verdicts this afternoon, Judge Jonathan Rose said his preliminary view was that the case falls into the category of a prison sentence between four to 10 years.
He said: "The defendant must understand there is a very high probability of a significant custodial sentence."
In a emotional statement released after the verdicts, Johnson's victim said the build-up to the trial has been "the hardest year of my life"/
She said: "I've had to face so much abuse after he claimed his innocence. I was made out to be a liar, if anything, I held things back because I didn't want all of this to come out.
"What happened in his car has turned my life upside down. I have lost all of my confidence. My school work has suffered.
"There are people out there who have made assumptions about me and that alone has been hard to deal with. I have been unable to defend myself publicly.
"The gossip on social media and hearing all of the horrible names that people have been calling me has been devastating to me, my friends and my family."
Johnson was bailed until he is sentence in two to three weeks time. The judge ordered he be under a curfew from 7pm until 7am.
Just before he left the dock, Judge Rose told Johnson that being released on bail meant he could get his "affairs in order".
He said: "You can say goodbye to your daughter. A prison sentence will mean you will not see her for some time."
Explaining his bail conditions, the judge said Johnson would be "well advised to stay well aware from social media".
The former England winger's career now lies in tatters and his former club Sunderland face questions over why he continued playing for them after he claimed he told them he had groomed, met and kissed the girl.
In a statement issued after the case, Sunderland FC said it "refuted" any suggestion the club knew all along that Johnson was intending to plead guilty to two charges.
The club also insisted it was not involved in tactical discussions about the timings of his pleas.
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Judge scolded Johnson
It can be reported for the first time today that Johnson was scolded by the judge during his trial for "discourteous behaviour" after he was seen joking with a security guard who sat next to him in the dock.
At the end of the second week of his trial, he was overheard saying to a friend: "I hope this is finished by Friday. It's a bit boring now."
Speaking after the jury's verdicts today, Det Insp Aelfwynn Sampson, of Durham Constabulary, said: "Adam Johnson was a Premiership footballer, an England International.
"He was living most schoolboys' dreams of playing professional football for his hometown club.
"However, Johnson exploited his position as a local hero to take advantage of a young and impressionable girl. This was not a case where he didn't know how old a girl was. From the start of their contact, he knew full well that she had just turned 15 and yet this did not stop him.
"The law is clear. The legal age of consent is set at 16 to protect young people. He no doubt thought that he would get away it, but today demonstrates that no one is above the law.
"We would like to thank the victim for her courage in coming forward and her family for supporting her through this incredibly difficult time over the 12 months it has taken to reach this conclusion."
An NSPCC spokesman said Johnson's "inexcusable" behaviour was made even worse by the fact he put his victim through the 'harrowing experience' of giving evidence.
The spokesman said: "Adam Johnson cynically used his celebrity status as a professional footballer to groom and sexually abuse an impressionable schoolgirl.
"Even though he was fully aware of her age he continued the relationship without any concern for the profound and damaging impact it might have on her.
"We hope she gets the appropriate help to recover from this dreadful episode and Johnson takes the time to reflect on how his predatory actions have caused so much anguish."
'Grooming in its purest form'
The trial heard the schoolgirl who Johnson groomed would wait outside Sunderland's stadium for him after matches and later befriended him on Facebook.
Johnson then sent her hundreds of messages on Facebook, WhatsApp and Snapchat, on which he created a secret account so his girlfriend, Stacey Flounders would not find out.
Following what the prosecution called "grooming in its purest form", Johnson twice picked her up in his Range Rover in January last year.
On the first occasion he signed football shirts for her, but later sent her messages asking for a "thank you kiss".
The jury found today that he sexually touched the girl on the second meeting. The trial heard he then dropped her off a sweet shop.
Police today released photos of the Range Rover Sport in which Johnson picked up the girl and committed the crimes. The vehicle had blacked-out windows and a personalised number plate.
Arriving at court today, Johnson was again accompanied by his ex-girlfriend Stacey Flounders, who has supported him during the trial and gave evidence for the defence, despite the couple having split up.
Today is a year to the day since Johnson was arrested at his mansion in Castle Eden, County Durham. Miss Flounders opened the door on that day.
The trial heard that, after his meeting with the girl, he looked up 'legal age of consent' online. He denied this was in relation to his meetings with the girl.
His defence has claimed the girl was a "proven liar" who made up the more serious allegations to "save face" in front friends she had told about Johnson.
The prosecution said Johnson has admitted lesser offences in a bid to get off the more serious charges. They claimed he has 'lied and lied again' to police and during his trial.
Judge Jonathan Rose finished his summing up yesterday by reminding the jury that Johnson deleted 834 WhatsApp message from his mobile phone.
He had it all
Sitting in his £2million mansion this time last year, Adam Johnson must have thought he had it all.
His glamorous girlfriend Stacey Flounders had just given birth to the couple's daughter and he was earning £60,000-a-week at his boyhood club Sunderland.
He was also the toast of the city after scoring a last-minute winner against bitter rivals Newcastle, prompting some fans to put models of him on top of their Christmas trees.
But the player's lavish stress-free existence was about to be blown apart when police arrived at his front door and, after speaking to Miss Flounders, arrested Johnson on suspicion of child sex offences.
After two months spent sending hundreds of sleazy messages to a schoolgirl he knew had just turned 15, his secret had been uncovered.
It would later emerge that, behind the facade of his happy family, Johnson had also been sending explicit messages to a number of other women.
A trial which has exposed Johnson's sordid lifestyle will now almost certainly end a footballing career which had promised so much.
- Daily Mail
