Soham detective Brian Stevens was today found guilty at the Old Bailey of conspiracy to pervert the course of justice. He was jailed for eight months.
His friend Crown Prosecution Service case worker Louise Austin was also convicted of the same offence. She was sentenced to six months, suspended for two years.
Stevens, 43, who was liaison officer to the family of Soham murder victim Jessica Chapman, was accused of giving police a false alibi to cover times when he was alleged to have downloaded "questionable images" on his Samsung laptop computer.
Stevens lied to police by saying he was staying at the home of his friend Miss Austin, 32, when the images were downloaded and that he did not have his computer with him at the time.
Miss Austin gave a statement to police supporting the alibi.
The jury of five women and seven men began their deliberations at 12.20pm on Wednesday at the end of a two-week trial.
Stevens, who has yet to be sentenced by trial judge Gerald Gordon, will now be dismissed or required to resign.
"Once he has been convicted of a serious criminal offence such as this the likelihood is that he will be dismissed," said Detective Superintendent Gary Ingrey, head of professional standards at Cambridgeshire Police.
"He could be required to resign, which is technically different. But either way the reality is that there will be little future for him."
Privately, officers from Stevens' force said he was arrogant, cynical and manipulative, and they felt "betrayed" by him.
They also expressed "disgust" that Stevens chose to use his dealings with the family of Jessica Chapman to try to convince the jury that he was an honourable detective.
During his trial a tearful Stevens had claimed he had to break the news of Jessica's murder to her family.
But the next day, during a dramatic courtroom exchange, the jury heard that in fact a colleague had told the Chapman's the bad news.Reuse content