A former trainee police officer who "harvested" victims from social media has been jailed for 15 years for rape and a string of sex crimes against girls as young as 13.
Mohammad Arshad was found guilty of 17 offences against 12 victims over a two-year period following a trial last month.
The 35-year-old was convicted of nine counts of causing a child to engage in sexual activity, three of sexual activity with a child and two of meeting a child following sexual grooming.
He was also found guilty of one count each of rape, causing a child to watch a sexual act, and paying for the sexual services of a child.
Arshad, of Luton, was a trainee police officer between April and October 2014 but was suspended when the mother of one of the victims came forward.
He was found to have "hundreds" of details of young girls, mainly from the Luton area, and was "obsessed with turning as many contacts with these young girls as possible into sexual encounters", Judge Jonathan Carroll said.
Jailing him for 15 years, with an eight-year extended licence period, at St Albans Crown Court, the judge said: "Between 2007 and 2013 you were actively and obsessively engaged in harvesting young girls' data from various social media sites, including BlackBerry Messenger, Facebook and WhatsApp."
The judge told a packed courtroom Arshad was "dangerous" and said he rejected the defendant's claim he had not known his victims were under-age.
He had also abused his position as a trainee police officer.
"For at least part of the period you were a probationary police officer - you used that to your advantage to impress your vulnerable victims and assure them they would be safe in your hands," the judge said.
The court heard Arshad had tried to befriend the girls, starting general conversations with them before later asking them to perform sex acts in exchange for money.
In one example, he offered one girl up to £500 to perform oral sex on him.
He also persuaded girls to go for rides with him in his car and offered them cigarettes and alcohol.
In another he asked a girl of 14 or 15 to come with him alone in the car before forcing her into the backseat and raping her.
The judge said Arshad had shown "total contempt" for the victim, saying he knew he was hurting her but "simply did not care at all".
"You became a honeypot surrounded by young girls," the judge added.
"You were not in control of your own behaviour - how far you went was determined by how far your victim was willing to go."
Arshad, wearing a blue T-shirt and black skullcap, showed no emotion as the sentence was handed down.
Police who searched Arshad's home found images of teenage girls on his phone and computers. Officers managed to trace a number of potential victims through social media messages.
Prosecutor James Newton-Price said Arshad sent graphic images and asked girls to have sex with him in the online conversations.
In impact statements, some of the victims described being taken advantage of, feeling "embarrassed and upset" and "physically sick" when they re-read the messages.
One said: "I would like to say I feel sickened by what happened. He abused my childhood and all the other girls trust and hurt them by trying to be our friend."
Angela Kerner, defending, said Arshad was "ashamed" of his behaviour but argued he did not pose a risk to the public.
She said: "He is accepting of his responsibility - he says he is ashamed and ashamed for his family as well.
"He fully accepts what Your Honour said in your summing up - he should have taken much more care, he should have taken more checks. He accepts your decision."
Arshad had contacted two of the girls during the period of his police training but all other contact had taken place beforehand, Ms Kerner said.
She added police found no evidence he had an "obsession with children".
Apart from the violence used during the rape, Arshad was "not a violent man", she said.
"He did not make any threats, there was no force, no intimidation. No girl was forced to get into his car, no girl was forced to meet him.
"Some communicated with him for considerable periods of time.
"Once refused, he did not push. He might have become a bit of a pest - he would spell out what he wanted and asked them what they wanted. A number of girls said he asked permission."
He was in an arranged marriage but seeking a divorce and had previously worked in Burger King, Pizza Express and as a CCTV operator in Luton and Barnet.
Arshad was given consecutive sentences of 10 years for rape and five years for causing a child to engage in sexual activity. He was given concurrent jail terms for each of the other offences.
He was also handed an indefinite sexual offences prevention order with conditions which included barring him from living with a girl under the age of 18, owning more than one mobile phone and deleting his internet browsing history.
Amanda Sawetz, senior Crown prosecutor for the Crown Prosecution Service, said: "Mohammad Arshad, formerly a police constable for Bedfordshire Police, groomed young and vulnerable girls, approached them through their friends and their social networks and systematically offered them money in exchange for sexual favours.
"The jury heard that his modus operandi was to make contact with the young girls on social media through BlackBerry Messenger, Facebook or WhatsApp. He gave the name of 'Waz', sometimes lying about his age, saying that he was 17 or 26 years old. He would sometimes use the fact that he was a police officer to gain the girls' trust but would reveal quite quickly to each of them his sexual intentions. On one occasion he raped a 14-year-old girl he had taken for a drive.
"We would like to thank all the young girls who gave evidence in this case and supported the prosecution. They did nothing wrong and were preyed upon by Arshad, who used their innocence and vulnerability to commit his criminal acts."