The doctors who will be evaluating whether Aurora theater shooting suspect James Holmes is sane don’t want Holmes’ lawyers watching over their shoulders during the examination.

In a letter sent Monday to the judge overseeing the case — and included in a prosecution filing made public Tuesday — the superintendent of the Colorado Mental Health Institute at Pueblo wrote that having one of Holmes’ lawyers present to observe the evaluation may bias the results.

“[T]he presence of third-party observers may compromise the validity of test results obtained during the course of the examination, and by extension, may compromise the reliability or validity of the results of the overall sanity examination,” the superintendent, William May, wrote in the letter.

Holmes’ lawyers have asked to be present during the evaluation “in order to advise Mr. Holmes about how to proceed during the examination and to ensure that his constitutional rights are protected.” Holmes’ lawyers made the request in a motion filed last week, one of a slew of motions the defense filed ahead of a deadline.

Holmes has been charged with 166 counts of murder, attempted murder and other offenses in connection with the July 20 attack on the Century Aurora 16 movie theater. He has pleaded not guilty by reason of insanity, and the judge in the case has ordered Holmes to undergo an independent mental-health examination, in accordance with state law.

Holmes is expected to be summoned to the state Mental Health Institute in the next month to undergo the evaluation. In his letter, May wrote the hospital has picked “an expert in forensic psychiatry” to conduct the sanity examination, but May said it is also believed the evaluation will come to include a psychologist and a neuropsychologist, as well. None of the experts chosen for the exam was named in the letter.

May said the hospital is concerned that having a “third-party” present for the evaluation could interfere with communication with Holmes or prompt him to seek approval from his lawyers before responding to questions.

“There is a risk that defense counsel would intentionally or inadvertently coach Mr. Holmes between evaluation sessions,” May wrote. “If this were to happen, the clinicians would be unable to assure the validity of the conclusions reached in the sanity examination.”

May wrote that interview portions of the evaluation could be taped, but he objected to recording any portions of the exam that use “testing materials.”

It is unclear how long Holmes’ evaluation will take. A hearing has been scheduled for August to receive the results, but that deadline could be extended if doctors say they need more time.

John Ingold: 303-954-1068, jingold@denverpost.com or twitter.com/john_ingold