A forensic pathologist testified that he could not ascertain the cause of death for Hong Kong Design Institute student Chan Yin-lam.

He also said though the teenager's hymen was intact, he could not verify whether she had been sexually assaulted.

On the seventh day of the inquest, Li Yuk-wah would not rule out the possibility of drowning, but said it was unusual for someone to try to kill herself by jumping into the sea if she knew how to swim.

He said Chan, 15, died within a day of going missing last year.

"Samples could not be taken for testing due to severe deterioration in the corpse's condition, which resulted in uncertainty over the cause of death.

"We cannot rule out closing the case with a drowning verdict," Li said.

Li performed an anatomy on Chan on September 24.

"The corpse was fully naked when it arrived," Li said.

"The corpse was visibly decayed, with no lesions, fractures, or intracavitary bleeding, which could explain her death," Li said based on the anatomy report, cowritten by two pathologists.

He said that based on known cases, the toxicology report and the anatomical examination, the cause of death could not be determined.

Li also said Chan's genital organs had no wounds, with her uterus and pelvis normal and her hymen intact.

"However, being sexually assaulted may not leave wounds on the private parts, so it could not be verified whether the deceased was sexually assaulted before death," Li added.

He could not explain why the corpse was fully naked, and noted there could be bruises covered up by livor mortis.

Wai Wing-kong, a government chemist, examined Chan's liver tissue, vaginal samples, and fingernails on both hands handed over by the police last September. He found blood on Chan's vagina, but no semen, and that the genes on the samples all belonged to Chan.

Wai also carried out genetic comparisons with Chan's mother, Ho Pui-yee, using an oral sample early this July.

The results showed their genetic relationship was "very strong," as among the 15 groups of the teen's genes, half of each group was inherited from Ho.

Coroner David Ko Wai-hung said there are seven ways to cause a corpse to float, including suicide, abandonment in water after being killed, being forced into water and suffocated, and entering water after taking drugs.

Li said there were no fatal injuries or self-defense injuries on Chan, and there were no drugs or poison in her body.

But due to corpse decay, blood could not be taken for an alcohol test, Li said.

Ko asked whether a person commit suicide by jumping into the sea with heavy objects if they knew how to swim.

Li said based on his experience, that did not happen often.

Chan Yin-lam

Li Yuk-wah

No clear cause of teen's death