Island County Prosecutor Greg Banks has decided he will not seek the death penalty against a 31-year-old homeless man accused of murdering both of his grandfathers at their North Whidbey homes last October.

Joshua Lambert is accused of stabbing to death his two 80-year-old grandfathers, George Lambert and August Eisner, on Oct. 3. Lambert, who is acting as his own attorney, pleaded not guilty by reason of insanity and told the Whidbey News-Times that he was in the midst of a hallucination when he committed the crimes.

“As horrific and devastating as his alleged crimes are, I have decided not to seek the death penalty against Joshua David Lambert,” Banks wrote in a statement. “My decision is consistent with the wishes of most of the victims’ surviving family members. It is consistent with the record of capital murder cases in Washington. And it is supported by the evidence known to me, and the law that governs its use at trial.”

Banks has spent months investigating whether to pursue the death penalty and announced his decision this week. He met with family members of both victims multiple times and discussed the case with some of the state’s most experienced death penalty prosecutors.

State law allows a jury to impose capital punishment when a person is convicted of aggravated first-degree murder, which is defined as premeditated first-degree murder where one or more aggravating circumstances exist. As Banks explained, aggravating circumstances include the fact of multiple victims where the murders are part of a single plan, or the fact that murders were committed in the course of a robbery or burglary.

“In the Lambert murder case, it is possible that a jury could find one or both murders were premeditated and that an aggravating circumstance exists,” Banks wrote.

Banks said he weighed a number of factors in making his decision not to pursue death. One is the strictly practical consideration of whether he would be successful.

Banks concluded it was highly unlikely that a jury would impose the death penalty because of Lambert’s mental state at the time of the murders, which can be considered a mitigating factor under state law. He said a News-Times story about a jailhouse interview with Lambert helped convince him that mental health issues could be considered a mitigating factor.

“The evidence regarding Lambert’s history and his behavior on the day of the murders convinces me that one or more jurors would find that to be a mitigating circumstance,” Banks wrote.

Statistics show that juries in the state are very reluctant to impose the death penalty, and even when they do, the appeals process can reverse the sentence or delay it for decades. Juries in the state have sentenced murderers to death only 32 times out of nearly 300 aggravated murder cases since the death penalty statute was enacted in 1981. Of those 32 death sentences, 17 murderers had their sentences reversed by higher courts. Of the other 15, six have been executed, one committed suicide, and eight remain on death row.

Banks also considered the wishes of the victims’ family members.

“A prosecutor must have an exceptionally strong rationale to pursue a capital prosecution, where doing so goes against the wishes of the victims’ families,” he wrote. “In my judgment, this case is not strong enough to go against the wishes of many family members.”

The prosecutor charged Lambert last October with first-degree murder in the death of George Lambert and first-degree kidnapping for allegedly tying up his great aunt with packing tape. Banks put off charging Lambert with the second murder until after he received a report on Lambert’s mental health from Western State Hospital. He received the report this week.

In an interview last week, Lambert said he was accused of assaulting three fellow patients while he was at the hospital. In one case, he said he was accused of stabbing a man in the ear and eye with a sharpened tube of a pen. He denies the assaults.

On Monday, Banks said he will ask the court to allow him to amend the charges against Lambert to two counts of murder in the first degree, one count of kidnapping in the first degree, three counts of burglary in the first degree, one count of taking a motor vehicle and one county of unlawful possession of a firearm. The murder and kidnapping charges will be filed as domestic-violence related charges with special allegations and deadly weapon enhancements.

If convicted of all the charges, Lambert would face 58.5 to 78 years in prison under the standard sentencing range, plus an extra 15 years for the deadly weapon enhancements.

Banks calculated that if Lambert is convicted of all the charges, the minimum time he will have to spend behind bars — taking “good time” into account — would be 71 years and eight months. Under state law, each murder conviction has a 20-year minimum during which time no early release or furlough can be granted and deadly-weapon enhancements are not eligible for good time credits.

While he’s not pursuing the death penalty, Banks said his goal is to make sure Lambert is never free again.

“The senseless brutality of the crimes has shocked and saddened our community,” he wrote. “It has inflicted incomprehensible pain on Joshua Lambert’s extended family — the families of the two murdered men.”