An Indiana man admitted to putting a poisonous "off-white powdery substance" into his wife's Coca-Cola so he could kill her and marry her daughter, according to state court records.

Alfred Ruf, 71, pleaded guilty to aggravated battery in July for trying to poison his wife. He was sentenced on Monday to four years in prison and five years of probation, Indiana court records show.

Ruf told officers in January 2022 that he had been "spiking" his wife's drinks over the last few months with a substance given to him by his wife's daughter, according to a probable cause affidavit obtained by USA TODAY.

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When deputies interviewed a then-69-year-old Ruf at the sheriff's office in January 2022, he told them that he was sexually involved with his wife's 31-year-old daughter from a previous marriage, the affidavit says. He then explained that his wife's daughter gave him the pill bottle with the powdery substance in September 2021 and instructed him to put it in her mother's drink, the court document continued.

Ruf was the only person charged in connection with the crimes.

Ruf told the deputies that the drug cocktail would make his wife go to sleep for "13 hours or so," the affidavit says. He also confessed that he put the drugs in the drink to "eventually kill (her)," according to the document.

The daughter and her female friend would call and tell Ruf to give the drugs to his wife, he told the deputies, per the affidavit.

"Alfred would then sprinkle some of the white powder in (his wife's) Coca-Cola can and then wait for her to fall asleep," the affidavit says. "(The women) would then come to Alfred's residence and put more of an unknown substance in (Ruf's wife's) drink and have her drink it."

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Once Ruf's wife was asleep, her daughter and her daughter's friend would put on a "show" for Ruf, according to the affidavit. The show involved the two women putting on Ruf's wife's negligees and then performing "sex acts on each other," the court document continues.

Ruf also told authorities that while he was having sex with his wife's daughter or her friend, one of the women would steal some of his wife's personal items. He also admitted to paying the women to perform sex acts, the affidavit says.

The victim's daughter told Ruf she wanted to "get mom out of the picture" once she found out they were selling their home, according to the affidavit. The victim's daughter also mentioned a life insurance policy to Ruf that her mother had in place, the court document says.

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Although Ruf acknowledged that he knew the drugs would eventually kill his wife, he also said he gave her the substance just so her daughter and her daughter's friend could come over and have sex with him, according to the affidavit.

Ruf came clean to his wife because he "felt bad," he told deputies, per the affidavit.