A former Portland high school teacher was sentenced Tuesday to 3 ½ years in prison after pleading guilty to child pornography charges brought years after he was first reported to police.

Phillip Lancaster, 36, was convicted of two counts of first-degree encouraging child sexual abuse. He knowingly duplicated “multiple visual recordings of sexually explicit conduct that involved children,” according to the Multnomah County District Attorney’s Office.

The charges came after police found “hundreds of child pornography images and videos” on Lancaster’s cellphone last year, with victims ranging from to 2 to 12 years old, the District Attorney’s Office said in a statement.

None of the children in the images have been identified, but none were students from Roosevelt High School, said prosecutor Bumjoon Park.

Lancaster, a language teacher, worked at the North Portland school until 2015.

Prosecutors initially charged Lancaster with 13 counts of encouraging child sexual abuse, but Multnomah County Circuit Court Judge Leslie Roberts dismissed 11 of the charges after sentencing Lancaster to 42 months in prison with credit for time served.

Lancaster also was sentenced to three years of post-prison supervision and five years of probation and must register as a sex offender.

Lancaster’s attorney, Joshua Pond, said his client had undergone a psychosexual evaluation that found he had a low risk of reoffending. He added that Lancaster was “capable of sticking to the straight and narrow.”

Lancaster spoke quietly when the judge asked if he had any comment.

“I won’t be seeking these materials and I hate that they were on my phone,” he said.

Police first searched Lancaster’s cellphone in 2014 when a 16-year-old Roosevelt student reported seeing Lancaster reach into the boy’s stall with a cellphone from underneath an adjoining stall. There is “no indication” that Lancaster’s phone contained any photos or videos of the student, according to Brent Weisberg, a spokesman for the prosecutor’s office.

But police did find “numerous child pornography files,” according to Park.

“Mr. Lancaster was trusted by the community to educate our youth,” Park said in a statement. “Instead, he made a horrible decision and seemingly attempted to capture a young boy in a state of nudity.”

However, no charges were brought against Lancaster until 2018, a four-year delay that the Portland Police Bureau said officers failed to investigate because of a faulty computer system that has since been replaced.

By the time the case was assigned a new detective last year, the statute of limitations had passed on the incident involving the 16-year-old, the prosecutor’s office said. But a grand jury indicted Lancaster in October on charges of encouraging child sexual abuse involving eight pornographic videos and five pornographic photos of a child on his cellphone.

Lancaster was placed on leave once the images were discovered in 2014 and resigned from teaching at Portland Public Schools in January 2015. His teaching license was never revoked and instead expired in October 2015.

Lancaster surrendered after learning of the indictment in 2018 and initially pleaded not guilty to the charges. He officially registered a guilty plea in June, admitting to possessing child pornography while “knowing and being aware of and consciously disregarding the fact that the creation of the visual recording of sexually explicit conduct involved child abuse,” according to court documents.

Pond, Lancaster’s attorney, declined to comment after the sentencing.

-- Diana Kruzman; dkruzman@oregonian.com; 503-221-5394; @DKruzman