Prosecutors in Tyler, Texas, say a man took part in "pure evil" by helping to run swingers' parties that allegedly forced young children to perform in sex shows.

Patrick Kelly is charged with engaging in organized criminal activity and aggravated sexual assault of a child.

Opening arguments began Tuesday with Smith County Assistant District Attorney Joe Murphy telling jurors that youngsters were "forced to do unspeakable acts."

One of the alleged victims — who is now 11 — has testified that she and other children had to do "nasty stuff."

A police report in Mineola, Texas, says officers first investigated a complaint about the alleged club in June 2005.

Kelly faces up to life in prison if convicted.