Robert Edward Dietz had a Starbucks habit.

On weekend mornings, the repeat sex offender settled into his regular seat at the coffee shop, his laptop open and his back to the wall, so no one could see him downloading child porn.

In late 2014, a Washington County sheriff's detective started showing up at the same time as Dietz.

Acting on a tip from another police agency, the cop was there to figure out who in the downtown Hillsboro coffee shop was downloading explicit videos of girls ages 3 to 12.

After several weeks, the detective landed on Dietz and realized he'd investigated the man before - in a 2009 child porn case.

Dietz was arrested at the Starbucks store one Saturday morning in December. Investigators seized his computer and found he'd been actively downloading more images moments before.

That account came from court records and Deputy District Attorney Paul Maloney, who outlined the case as Dietz pleaded guilty Thursday in Washington County Circuit Court to five counts of first-degree encouraging child sex abuse.

Dietz's criminal history included 1996 convictions for first-degree sodomy and first-degree sex abuse and child porn convictions stemming from the 2009 case.

Facing a maximum of life in prison, Dietz, a slight man who wore an orange jail jumpsuit and a bushy white mustache, signed a plea deal that sent him to prison for 15 years.

Defense lawyer Bill Redden offered no commentary on his client.

Did Dietz wish to add anything?

"Uh, no, your honor," he said.

"There really isn't much to say in this case," Presiding Judge Charles Bailey said, "other than you have a serious issue, and maybe this is the only way we can keep society safe."

-- Emily E. Smith

esmith@oregonian.com

503-294-4032; @emilyesmith