Suspected double-murderer Joshua Lambert led detectives to a hidden shotgun for $50 and offered to write a confession for another $50 and a cup of coffee.

Those details are included in a Motion in Support of Admission of Defendant’s Statements that Island County Prosecutor Greg Banks filed in Superior Court last week.

Banks is asking the judge to allow him to present at trial a number of allegedly incriminating and unusual statements made by Lambert.

Lambert, a 31-year-old homeless Oak Harbor man, is facing two counts of first-degree murder and one count of kidnapping for allegedly murdering his two grandfathers and tying up his great-aunt in October 2011.

He is acting as his own attorney and is claiming he’s not guilty by reason of insanity. His trial is set for March 12.

On Dec. 21, 2011, Lambert sent a letter from his jail cell to Detective Ed Wallace with the Island County Sheriff’s Office.

He suggested he may know the whereabouts of a sawed-off shotgun missing from the home of one of the victims.

He offered to provide information in exchange for $50, Banks wrote in the motion.

Lambert drew a map to help the detectives find the gun.

The next day, the detectives brought Lambert to the wooded area in Oak Harbor to help look for the gun.

They eventually found it nearby and Lambert got his money.

A month later, Lambert sent another unsolicited letter to Wallace, offering to provide “a written confession to the two murders for $50 and a cup of coffee and maybe another folder like the one that the discovery came in, but the folder is negotiable,” Lambert’s letter states.

He sent another letter the next day offering to testify in court that he committed the alleged homicides for an additional $50, the motion states.

A few weeks later, Lambert provided the prosecution with a five-page, hand-written confession.

Wallace said Lambert got the money and a cup of coffee.

In addition, Banks wrote that he plans to present statements that Lambert allegedly made to an Oak Harbor police detective and the jail chief.

After the Oak Harbor police arrested him in the middle of N. Oak Harbor Street Oct. 3, 2011, a detective asked him whether he had any weapons, needles or anything sharp on him. Lambert allegedly stated that he had some needles, but that he believes he dropped or lost “the knife,” Banks wrote.

A few weeks later, Lambert allegedly told the jail chief that he had “killed people,” the motion states.