FARMINGTON (AP) — A Maine judge has ruled to limit a psychiatrist’s testimony on whether a Massachusetts man charged with killing an elderly Farmington woman was under the influence of the drugs at the time of the slaying.

Juan Contreras of Waltham, Mass. has pleaded not guilty to the June 2011 stabbing death of 81-year-old Grace Burton.

A judge last week ruled on the state’s motion to exclude the testimony Dr. William Brennan because it improperly refers to the defendant’s character, is irrelevant unless the defendant testifies, and because Brennan lacks the qualifications to say whether Contreras ingested the drug ‘bath salts.’

The Sun Journal reports the court ruled that if the defense uses Brennan as a witness at November’s trial, he would be allowed to testify only about the use of bath salts.