Questions are to be expected when a suspect dies in police custody. In the case of Lam Wing-chun, who allegedly hanged himself in a cell after being arrested in a high-profile rape and robbery case, there are unusual details that point to security loopholes and human negligence. A comprehensive investigation and overhaul of the relevant rules and procedures are needed to prevent a recurrence.

Exactly what went wrong will be a matter for the coroner’s court to find out. According to a police source, the 48-year-old man might have snatched a computer cable without being noticed while he was being interrogated at Sau Mau Ping police station. There were suggestions that he sought to hang himself from a sprinkler, triggering a fire alarm at 3am on Thursday. After being removed to another cell, he was found hanged at about 9am, shortly after a routine inspection, according to media reports.

As a matter of procedure, all suspects undergo a body search before confinement to prevent assaults and self-injury. There are also regular cell inspections by duty officers. It is therefore baffling that Lam could take his life under such circumstances.

The explanation by police chief Stephen Lo Wai-chung on Thursday did little to clear the air. Understandably, he cannot divulge too much detail ahead of the inquest. But the force has rightly responded to public concerns by tasking the crime unit of another region to take over the investigation. Hopefully, this will instil confidence in a fair and thorough investigation.