A Washington state couple kept two young autistic boys in a dark room with a cage-like door for convenience, prosecutors told jurors Monday while the defense countered that the child-proofing was intended to keep the children from harming themselves.

The opening statements came as the trial of John Eckhart, 31, and Alayna Higdon, 27, opened in Clark County Superior Court. The Vancouver couple are charged with unlawful imprisonment of Eckhart's sons, ages 5 and 7, between October 2010 and April 2011.

Deputy Prosecutor Dustin Richardson said Eckhart was known to take hours-long smoking breaks, leaving the boys' 9-year-old older brother to watch them, The Columbian reported (http://is.gd/yRAMQO ). The prosecution also said the father played video games during the day. Higdon, a college student, was away from home most days.

However, defense lawyer Jon McMullen said the makeshift door was Eckhart's effort to increase the apartment's child safety after less-restrictive measures failed.