TAIPEI (Taiwan News) — A DNA test conducted on an old cigarette butt helped investigators find and charge the suspect in a murder committed 22 years ago, reports said Friday (Dec. 23).

A woman named Pan (潘) was found stabbed to death near an alley in Taoyuan City in July 2000, the Liberty Times reported. The evidence from the crime scene, including the remains of a cigarette and a piece of tissue, were kept, even though at the time, investigators did not find them useful.

Thanks to technological progress, a recent review established a DNA connection with a convicted drug offender named Chiu (邱). When police visited him with a warrant on Dec. 14, he initially denied having killed Pan, but when he was taken to the alley, he admitted the accusation, per the Liberty Times.

Pan was reportedly a prostitute who angered Chiu with her complaints about his performance. He later attacked her with a knife in the alley and threw the weapon into a ditch where cameras could not observe him, the report said.

Pan lived in New Taipei City, but in order to afford a university education for her daughter, she traveled by train to Taoyuan City each day. There she rented a room near the station and tried to find clients, according to an investigator.