The Tokyo High Court on Wednesday upheld the death penalty for a 39-year-old woman found guilty of killing three men in 2009 — a conviction based mainly on circumstantial evidence.

According to the initial ruling at the Saitama District Court in 2012, Kanae Kijima killed Takao Terada, 53, in January 2009, Kenzo Ando, 80, that May and Yoshiyuki Oide, 41, that August.

Kijima, who maintained her innocence, had been romantically involved with each of the victims and was convicted of killing them in order to avoid having to pay off her debts.

While prosecutors said all three men died of carbon monoxide poisoning from coal briquettes burning in stoves in unventilated locations that Kijima prepared, her defense team argued the men had either committed suicide after arguing with her over breaking up or had died by accident. Many people commit suicide by this method.

Accepting the prosecutors' claim, the district court ruled that she "committed the crimes so she could maintain a luxurious life."

The lay judges for the trial served 100 days, the longest period since the system was introduced in 2009.