A former Wisconsin sheriff's deputy with Lou Gehrig's disease has been found not legally responsible in the killing of his wife and sister-in-law. Forty-year-old Andrew Steele had pleaded not guilty by reason of mental disease to two counts of first-degree intentional homicide in the August 22 shooting deaths of his 39-year-old wife, Ashlee Steele, and her sister, 38-year-old Kacee Tollefsbol of Lake Elmo, Minnesota. Defense attorneys argued that the disease damaged Steele's brain, making him not criminally responsible for the deaths. Scroll down for video . Former Wisconsin sheriff's deputy Andrew Steele, pictured in court earlier this month, has been found not legally responsible in the killing of his wife and sister-in-law on Thursday . This undated photo provided by Rachelle Putnam shows Ashlee Steele, left, and her sister, Kacee Tollefsbol, both were found dead of gunshot wounds at Steele's home in Fitchburg, Wisconsin, last August . A jury deliberated for about 10 hours until all but two of the 12 agreed the verdict early on Thursday. During Steele’s trial earlier this month forensic psychiatrist Dr. Doug Tucker had testified that a rambling note Steele wrote about suicide and sexual relations with his wife and sister-in-law was delusional and showed Steele's brain was deteriorating because of ALS. Tucker said that was the reason Steele killed the two and that he was 'unable to conform his conduct to the law.' The defendant had claimed he blacked out during the killings. Steele had been diagnosed with the progressive neurodegenerative disease last June. Lou Gehrig's disease, also called amyotrophic lateral sclerosis, or ALS, attacks motor neurons, cells that control muscles. Prosecutors believed Steele planned the killings. The State had asked all witnesses if Steele had memory issues before that day in August, and they all said no. Defense attorneys argued that Lou Gehrig's disease had damaged Steele's brain, making him not criminally responsible for the deaths . Family: The couple, pictured, had two children, and had been together for 26 years . In a mostly incoherent, stream-of-consciousness letter written by Steele the day before the murders, the former deputy claimed he had had a sexual relationship with his sister-in-law and enjoyed 'numerous threesomes' with Kacee and his wife, reported the station WIBA. The typo-riddled note also stated that when Kacee and Ashlee learned of his ALS diagnosis, they proposed a suicide pact. According to Steele, the women wanted to jump off a cruise ship together, poison themselves with carbon monoxide inside a car, or shoot themselves with his service weapon. 'See you all on the other side,' the note concluded. The missive was last edited on Steele’s phone just after 6am on August 22. About seven hours later, a mortally wounded Kacee Tollefsbol called 911 saying she and her sisters had been shot. Dr Tucker testified that there was no evidence to support Steele's claims that he had been in a three-way relationship with his wife and sister-in-law. Friends of Kacee Tollefsbol also said in court that her and Steele's relationship did not go beyond that of a brother and sister, reported Wisconsin State Journal. Tearful testimony: The slain sisters’ third sibling, Hailee Mesiterling, said from the stand that Andrew Steele was in love with his sister-in-law . However, the slain sisters’ surviving sibling, Hailee Mesiterling, said from the stand that Andrew Steele was in love with Tollefsbol and acted inappropriately towards her during a family vacation last summer. Steele’s defense attorney, Jessa Nicholson, had told the court that her client maintained that on the day of the killings he and Ashlee had sex involving bondage, and a zip tie accidentally fastened too tight around her neck, according to WKOW. Steele’s last memory from that day, according to his attorney, is of him trying to find a pair of scissors to cut the restraint around his wife’s neck. He then blacked out and awakened later in a hospital bed with a tube down his throat. Unable to speak, the 40-year-old wrote notes asking if he had been in a car accident and inquiring after his wife. ALS: Andrew Steele, pictured in court in 2014, penned a rambling note a day before the killing claiming that he had had threesomes with his wife and sister-in-law, and that the three of them had made a suicide pact . Andrew Steele is wheeled out of his home in a stretcher after allegedly murdering his wife and her sister on August 22 . If the jury had found him responsible for the double-homicide, Steel could have faced up to a life sentence without parole. Ashlee Steele, 39, was found shot in the head in the master bedroom and cops found Andrew Steele sitting in a laundry room with a pistol. The former deputy had started the dryer and vented it back into the room and he had set up a grill loaded with hot charcoal in the room in a possible suicide attempt by carbon monoxide. The killings came just days after the victims and the suspect's friends took part in the ALS ice bucket challenge, raising $23,000 towards the ailing deputy's medical expenses. In his letter, Steele lamented that collected funds were not enough to cover their family's expenses. Between the two of them, the slain sisters have left six children behind.
Former Wisconsin sheriff's deputy Andrew Steele, 40, has been found not legally responsible in the killing of his wife and sister-in-law . He shot dead wife Ashlee Steele, 39, and her sister Kacee Tollefsbol, 38, on August 22 . His defense team had argued that Lou Gehrig's disease had damaged his brain, making him not criminally responsible for the deaths . Prosecutors believed Steele had planned the killings abnd a third sister said he had displayed inappropriate feelings towards Tollefsbol .