Yang Hong-ru was known to both victims, Chen and Lai. He may have harboured murderous intent towards the two men, possibly due to gambling debts or other motives.
Under the pretence of going on a trip or visiting friends, Yang drove away with the victim Chen on the morning of 27 June 2015, and with the victim Lai on the morning of 12 July that same year. On both occasions, during the journey, Yang laced the victims' food and drink with sleeping pills, rendering each of them unconscious. He then placed them head-first, feet-up, into sealed metal drums, where they suffocated to death within the confined spaces.
He transported the drums containing the victims' bodies to a location near the boundary between Nantou and Hualien on Provincial Highway No. 8—the first on the afternoon of 27 June 2015, and the second at midday on 12 July, where he disposed of them by pushing them into a ravine, thereby killing Chen and Lai in succession.
In the first, second, and third trials, as well as the first retrial, the defendant was sentenced to death. This was later commuted to life imprisonment in the second retrial, and that sentence was ultimately upheld by the Supreme Court.
In addition to the psychiatric assessment, a pre-sentencing social investigation was also conducted in this case. A multidisciplinary team was assembled for this purpose, comprising not only psychiatrists and psychologists, but also legal scholars and criminologists.