An 88-year-old man who was arrested shortly after the death of his ailing wife on suspicion of aiding in her suicide will not be charged with any crime.

San Diego prosecutors determined that the case against Alan Purdy couldn't be proven beyond a reasonable doubt, said Tanya Sierra, a spokeswoman for the district attorney, on Wednesday night.

Margaret Purdy, 84, was found dead in her home with a plastic bag over her head in March, her death ruled a suicide by the county medical examiner. Family said she had becoming increasingly depressed as she battled a series of ailments and injuries in her final years while her husband doted on her.

"She had mentioned for some time that she was under a great deal of pain and that this was a very hard life," the couple's son-in-law, John Muster, said in a telephone interview from Berkeley at the time of the arrest.

The once vibrant woman left a suicide note on her desk after being bedridden in her final years from severe pancreatitis, as well as an autoimmune disease, a crumbling spine and three fractured vertebrae that never healed, The Los Angeles Times reported.

Alan Purdy's sister-in-law, Margot Smith, told The Associated Press Wednesday that it would have been awful if prosecutors had decided to pursue a case.

"I'm absolutely delighted to hear it. He's 88 years old and hard of hearing and he loved his wife dearly," Smith said.

Smith added that Alan Purdy was so hard of hearing that he had trouble making out what authorities were saying to him at the time of his arrest.

"I'm delighted to hear this," Purdy's daughter, Catherine Purdy, a Berkeley psychologist, told The Times. "I feel like justice has finally happened."

The Purdys were close friends for many years and proved a perfect match when they married later in life, relatives said. It was the second marriage for both Purdys, each of whom had outlived their previous spouses, said The Times. Margaret Purdy kept a close eye on her husband, who lost much of his hearing with age. He, in turn, watched after her as she coped with her ailments.

A previous suicide attempt

In Margaret Purdy's last year of life, her pain became so severe that she was unable to get out of bed without Alan's help, and she stopped doing activities that she enjoyed, like painting, The Times reported in May. Three months before her death, when Alan was out of the house, Margaret had attempted to take her life by poisoning herself with carbon monoxide in their garage; Alan came home and pulled her out of the car before she could finish, The Times said.

Alan Purdy, a pilot with a doctorate in biomedical engineering, worked for years at the federal Occupational Safety and Health Administration, and Muster said both were "fully functioning mentally."

When paramedics arrived at their home on March 20, Purdy told them his wife had taken 30 sleeping pills crushed in applesauce, then suffocated herself, The Times reported. He told them -- and later deputies -- that he didn't help her, but he also said he didn't try to stop her.

From the bedroom that he and Margaret shared for nearly 15 years, Purdy admitted to The Times, "Yes, I sat beside her as she died. I didn't want her to feel abandoned. I wanted her to know that I loved her."

There is no specific federal law regarding either euthanasia or assisted suicide. All 50 states and the District of Columbia prohibit euthanasia — which is when a doctor actively kills a patient — under general homicide laws.

California is one of three dozen states that have specific laws prohibiting assisted suicides. Seven ban assisted suicide under common law.

The Associated Press contributed to this report.

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