Man claims sister was poisoning him, leading to murder: Court docs

PORTLAND, Ore. (KOIN) -- A man who was arrested after police said he admitted to killing his sister, claimed that his sister had been poisoning him for months, court documents said.

Dwayne Robinson was arrested on the night of Wednesday, Sept. 18 after a disturbance with a weapon report brought authorities to his home in Vancouver.

According to a probable cause document obtained by KOIN 6 News, Clark County deputies were called to the home just before midnight by a man, who reported that Robinson, his ex-brother-in-law, had stabbed his sister Diane to death.

As deputies arrived on the scene, the documents said that they spoke with the man who claimed that he had come to check on his ex-wife who he was still on friendly terms with.

When the man arrived at the home, he said he met Robinson, who told him that he "wasn't welcome there." When the ex-husband asked where Diane was, he told investigators that Robinson told him that he had stabbed her to death.

The documents then say that deputies surrounded the home and contacted Robinson, who came out of his garage and surrendered.

Five deputies entered the home and said they found Diane dead in the kitchen covered in a blanket, her body showing signs of violent trauma, but the cause was still unknown.

Following the arrest, deputies said they interviewed Robinson who told them that his sister had been poisoning him for years which he claimed led to depression, sadness and pain.

Robinson told deputies that he grew tired of being poisoned so he decided to kill her around Sept. 15 using a hunting knife, according to court documents.

On the day of the murder, documents said Robinson said he found Diane eating in the kitchen and stabbed her four times, leading to her death.

He then said he covered her with a blanket and proceeded to eat her food because it wasn't poisoned.

Robinson was booked on a first-degree murder charge. He is expected in court on Monday, Sept. 23.