Image copyright York County Police Image caption Lana Clayton, 52, had previously shot her husband in the head with a crossbow, police say.

A South Carolina woman has been charged with murder after allegedly poisoning her husband by putting eyedrops into his water for several days.

Lana Clayton, 52, was arrested weeks after her husband, Stephen Clayton, 64, was found dead at home.

She was detained when a toxicology test discovered a chemical called tetrahydrozoline in his body.

The substance is found in over-the-counter eyedrops and nasal sprays that are available without a prescription.

On Friday, York County police also charged her with unlawful malicious tampering of food between the dates of 19 and 21 July, when the alleged murder occurred.

In a statement, police say she admitted to poisoning her husband "without his knowledge".

She was arrested and held in custody on Friday. Police have not announced any potential motive.

Mr Clayton, who founded a physical therapy company, was pronounced dead after appearing to suffer a fall down stairs in the foyer of his home in the upmarket neighbourhood of Clover - about 20 miles from Charlotte, North Carolina.

A funeral was held for him in the couple's backyard in early August - friends and neighbours say - before investigators discovered his cause of death.

According to the Herald newspaper, Mrs Clayton has no previous criminal record, and has not been arrested before.

Prosecutors say they are now reviewing a 2016 incident, in which she shot her husband in the head with a crossbow as he slept.

Police determined that that shooting was "accidental", according to a police report obtained by the Charlotte Observer.

Investigators found Mrs Clayton at home "crying and upset" after the crossbow incident, according to the report.

She said at the time that her husband was mentally abusive to her, and had "mood swings" but never physically hurt her.

Tetrahydrozoline can cause seizures, stop breathing and induce comas, according to the US National Library of Medicine.

Even a few drops of the drug, which is intended to reduce redness, can cause "serious adverse events".

The couple had been together for eight years, friends told WSOC-TV. Others added that she was known to attend the neighbourhood Bible study group.

Mr Clayton's family told the station that they were "shocked and mortified at the cause of Steven's death".

"All of our family and friends know how much he loved his wife, Lana, and how devoted he was to her. We are all still trying to process this."

According to the York County Probate Court, Mrs Clayton was appointed to represent Mr Clayton estate after his death.

Mrs Clayton's Facebook page states that she worked for the US Department of Veterans Affairs in Charlotte.

Their home, worth about $800,000 (£620,000), was modelled on the Mount Vernon estate of the first US President, George Washington.

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