POLICE have defended their failure to prosecute a pervert before he groped another teenage girl on a bus.

Christopher Swift sexually assaulted a 17-year-old girl on the Oxford to Kidlington bus in November 2011.

The victim’s mother gave a bag of her clothes to detectives but the case was not solved until after Swift struck again on the same bus service in September last year.

Swift, 62, of Matthew’s Way, Wootton, near Abingdon, was found guilty of sexual assault on Tuesday after a two-day trial in Oxford Crown Court.

The trial heard he sat next his first victim on an afternoon in November 2011 on a journey from Oxford city centre to Kidlington.

He laid his coat across her lap and then placed his hand on her leg for around 10 minutes, before moving it towards her crotch.

Peter Du Feu, defending Swift, said the girl’s mother bagged up the clothes she was wearing that day and handed them to police.

Addressing the jury, Mr Du Feu said: “We are not sure where that clothing is, it has not been produced to you.”

He added later: “She was not asked to set her account in aspic until October 2012, and by then a lot of water had passed under the bridge.”

Nine months later, Swift sexually assaulted a 16-year-old in September 2012 while riding on the same bus.

On that occasion his young victim told police she “swatted” his hand away when he moved it towards her “private parts”.

Giving evidence during his trial on Tuesday, the retired man was challenged to explain why he made so many journeys on public transport and he said: “I just enjoy travelling by bus.”

He repeatedly denied he had touched either girl on purpose.

Summing up his client’s case, Mr Du Feu said Swift admitted he was “odd” and could even be considered “creepy” by some people.

He also criticised the police for how they handled the investigation.

But Naomi Perry, prosecuting, said Swift was really “looking for girls to touch” when riding on buses and would change buses repeatedly until he found one.

She said during her summing up speech that both girls had been “credible” witnesses when they gave evidence. She told the jury: “They were upset, they were on their way home and they were crying and they told their mums.

“These girls are not exaggerating, they have come to the court to let you know what happened.”

The jury took around two-and-a-half hours to unanimously find Swift guilty of both counts of sexual assault.

Thames Valley Police spokesman James Williams said after the case that Swift’s first crime was “thoroughly investigated” by the force and Swift was interviewed.

He said the victim’s clothes were tested but no DNA was found. He also said CCTV images were not clear enough to make a positive identification.

Swift was released on bail and will be sentenced on July 18 after a pre-sentence report has been prepared by probation officers.