Pharma researcher allegedly killed wife by making her drink methanol

The Yomiuri Shimbun
Keisuke Yoshida is seen under arrest Friday.

A researcher at a pharmaceutical giant was arrested Friday on suspicion of murdering his wife by having her ingest toxic methanol at their home in Tokyo in January.

According to a senior official of the Metropolitan Police Department, Daiichi Sankyo Co. employee Keisuke Yoshida, 40, is suspected of murdering his wife Yoko, then 40, possibly by mixing methanol into liquor at their home in Ota Ward, Tokyo, sometime between Jan. 14 and the morning of Jan. 16.

Yoshida called for an ambulance on the morning of Jan. 16 and told paramedics he found his wife unconscious when he woke up. The MPD initially thought Yoko died of an illness as she had no obvious external injuries, but an autopsy found she died of acute methanol poisoning.

Methanol is a type of alcohol, and Yoshida, who is in charge of drug development at his office, is believed to have sometimes used methanol to clean equipment.

He denied the charge immediate after his arrest, saying he never brought methanol into his home. But he reportedly then began refusing to respond to questions.

The MPD suspects that Yoshida may have mixed methanol into the liquor and made Yoko drink it. Yoko is believed to have had symptoms such as vomiting on the morning of Jan. 15, suggesting she may have ingested methanol from the night of Jan. 14 to the early hours of Jan. 15.

Yoko used to work at Daiichi Sankyo, too, and the pair married in 2010. They bought an apartment in 2013, where they lived after their son was born.

Yoko moved to an advertising company after quitting Daiichi Sankyo, and her career was reportedly stable.

According to investigative sources, however, the couple had been on bad terms for several years over Yoshida having an extramarital relationship, among other problems. They are said to have lived separate lives under the same roof and to have eaten their meals separately.

Several videos showing their arguments were found on Yoko’s smartphone.

In a voluntary interview with police before his arrest, Yoshida is said to have admitted to being on bad terms with his wife and said he sometimes raised his hand against her.