RAMSTEIN AIR BASE, Germany — An Air Force staff sergeant who advertised his baby-sitting services to the Kaiserslautern military community and touted his compassion for children in an online forum pleaded guilty Thursday to multiple counts of raping and molesting three young girls in his care over the last year.

Joshua Adam Smith, a staff sergeant with the 86th Aircraft Maintenance Squadron at Ramstein Air Base, faces a maximum potential sentence of life in prison without parole for his crimes against the children, ages 3, 4 and 8.

Officials would not reveal whether they suspect Smith of having molested other children at Ramstein or on other bases where he has been stationed, including Incirlik Air Base in Turkey and Offutt Air Force Base in Nebraska.

But in a posting last year under the name “Joshua” on the Ramstein Underground Internet forum — which military prosecutors entered into evidence against Smith — the sergeant boasted of having worked with children “since I was 13” and having been a baby sitter for many years in multiple locations.

“Been babysitting here for about a year, mostly to coworkers and good friends,” Smith wrote on the website. “But I’m trying to reach out further because its hard to find jobs.”

At a court-martial Thursday, Smith pleaded guilty to 18 criminal counts, including anal and genital penetration and penetrating the children with objects including a Sharpie marker and a plastic tube.

He also pleaded guilty to photographing and videotaping his victims, while posing them in a sexual manner and performing sexual acts on them.

According to the charging documents in the case, the crimes against the three victims occurred between November 2009 and April 30 of this year, when Smith was placed in pre-trial confinement at Mannheim.

Air Force records indicate that Smith joined the Air Force in 2001 and arrived at Ramstein in December 2007.

Prosecutors did not offer Smith a plea agreement. He’s expected to be sentenced Friday by Col. Dawn Eflein, the chief military judge for the European region.

Dressed in his Air Force blues, Smith spent several hours Thursday morning describing his crimes in military court, speaking with a sure, steady voice.

“I did it for my own sexual gratification,” he confessed.

He also said he was not under the influence of drugs or alcohol when he committed the crimes.

Smith told the court that he initially communicated with two of the victims’ mothers online, when they sought out his baby sitting services.

“I offered my services and they agreed,” he said, noting that he even provided references.

Some of the criminal acts occurred at the victims’ off-base homes and some took place at Smith’s military housing unit on Vogelweh, prosecutors said.

One victim was a German national. Another has a father in the Air Force.

Some of the parents of the victims were expected to testify Friday during sentencing.

Not revealed in court Thursday was how Smith was discovered. Evidence against him includes photos and videos he made of two of his victims, and numerous computer files containing child pornography.

In his online postings, Smith attempted to address the fears that parents sometimes express about male baby sitters. At one point, he offered advice to parents to be vigilant.

“One thing that I do want to point out to all parents out their, is that ANYONE could be a possible abuser, not just males or strangers,” Smith wrote. “...It doesn’t mater WHO you have baby-sitting. A male, female, grandmother, grandfather, friend, whoever, doesn’t matter. LISTEN to your child, they will tell you if anything is wrong. And follow that wonderful motherly instinct that you all have, If something feels wrong, its possible that it is and you should probably look into it.”

svanj@estripes.osd.mil