A 28-year-old former youth pastor who had a yearlong affair with a 15-year-old girl from his Venice church was sentenced Oct. 18 to four years, four months in state prison.

Demetrius Allen, of Granada Hills, who served as youth pastor at the First Baptist Church of Venice, pleaded no contest in September to three counts of lewd act on a child, county district attorney spokeswoman Jane Robison said.

Following the sentencing, San Fernando Superior Court Judge Cynthia Ulfig said Allen must register as a sex offender for life after he completes his prison term, said Deputy District Attorney Cathy Lee, who prosecuted the case.

Allen was arrested by Los Angeles Police Department Devonshire division detectives Aug. 3 following an extensive investigation into multiple allegations of sexual misconduct with underage girls who attend the First Baptist Church. He served as the pastor in charge of youth ministries at the church in the Oakwood neighborhood of Venice.

Police said Allen was involved in a sexual relationship with a 15-year-old female member of the church that began in March 2010 and continued through May of this year. The relationship did not occur in Venice, police said.

Lee said Allen resigned his church post in August after he was arrested and charged with 10 counts of lewd act on a child, one count of possession of child pornography and one count of contacting a minor for sexual offense, all felonies. In exchange for his plea, the remaining counts were dismissed Oct. 18, Robison said.

The LAPD conducted the investigation.