A Lawrence man charged with murdering his girlfriend’s 3-year-old daughter plans to rely on a “voluntary intoxication” defense, his attorney said Tuesday.

The trial for Jason W. Dillon was scheduled to begin later this month in District Court, but it was postponed Tuesday until Jan. 17. Defense attorney Mark Manna told Judge Michael Malone that a witness crucial to the voluntary-intoxication defense has joined the military and was unavailable.

Dillon is charged with killing Sydni C. Perkins June 19 in the 1100 block of George Court. He was baby-sitting the girl while her mother was at work and told police he’d consumed 16 beers the night before and was out until 6 a.m.

According to police, he admitted shaking Sydni after she refused to help pick up laundry, and striking her in the back of her head more than a dozen times after she told him she didn’t want him to be her daddy anymore. Manna has said he doesn’t plan to dispute that Dillon caused Perkins’ injuries but that he will argue his client wasn’t capable of acting intentionally.

Dillon is scheduled to be back in District Court on Thursday morning for another hearing on pretrial motions.