Following a preliminary autopsy, police asserted that no foul play was suspected and that Chan had killed herself,[1] in part due to her known history of mental illness, psychosis, self-harm and attempted suicide.

[2][3][4][5] The coroner's inquest concluded with the jury unanimously returning an open verdict, after Magistrate Ko Wai-Hung ruled out both homicide and suicide as possible causes due to insufficient evidence to support this.

[11] According to surveillance footage from Youth College she attended, she left the campus barefoot and walked towards the waterfront near Tseung Kwan O on 19 September.

Police initially reported that the victim was a female suspected of being between 25 and 30 years of age, 1.5m in height, medium build, with long blond hair.

[13] The police originally requested a court warrant on 27 September on the grounds that the case was a murder, but changed the categorisation to "dead body found" (not suspicious) several days later.

Masked protesters accused the school of downplaying the situation; they continued to damage facilities and equipment on campus for two days, with the police ended up having to be called.

[18] Online rumours suggested that the girl in the footage was an imposter,[3] and that an actress had appeared in some cover-up by authorities (although there is little evidence to support this claim).

[1][19] Suspicions were stirred at the apparently hasty cremation of Chan's body soon after the death, but the police countered that the coroner had authorised the process.

Beh agreed that Chan's body had been hastily cremated, and urged police to release further information about the autopsy and for a coroner's inquest to be undertaken.

[21][22] In an interview with TVB News on 17 October, Chan's mother, Ho Pui-yee, said that after looking at all the relevant CCTV footage, she believed that her daughter's death was a suicide.

[27] On 24 August 2020, two people were arrested for public order offences after a crowd harassed Ho as she left the Coroner's Court hearing.

[28] A coroner's inquest took place in late August and early September 2020 to investigate the cause and circumstances of Chan Yin-lam's death.

[30] As expert witness, the forensic psychiatrist Robyn Ho (Ho Mei-yee) said that Chan appeared to show symptoms of multiple mental illnesses and that her symptoms (such as her confused state of mind, capricious behaviour, and complaints about hearing non-existent voices) suggested that she suffered from an early stage of psychosis, a condition that brings a higher risk of suicide and may result in difficulty with body coordination during an episode.

[3][33] They noted the failure of the Hospital Authority to effectively follow up on cases of teenagers with mental health issues, especially after the inquest heard that Chan might have developed psychotic symptoms a month before her death.

"[34] After her class ended at 1 pm, Chan was clearing her school locker for half an hour and said to Chiu that she would return to the Tseung Kwan O campus that night but did not give a reason for it.

[35] Leung Po-yi, the HKDI administrative officer, said that Chan's belongings—including an identity card, a student ID, a mobile phone, and an Octopus card—were turned in later that night.

[37] Chow Tai-lai, a taxi driver, claimed that Chan got into his car and asked to be driven to a construction site next to LOHAS Park MTR station, a few hundred metres from a promenade, on that night.

[3] The jury could not verify the veracity of Chow's statement in the absence of corroboration,[3][33] and concluded that Chan last appeared inside Tiu Keng Leng station after 7 pm on 19 September 2019.

[43] Wai Wing-Kong, a chemist, found no conclusive evidence that Chan was sexually assaulted, as there was no DNA from another person in the vagina or under the fingernails.

[44] Lee Wing-Man, a laboratory technologist, said that she found no fabrics inside Chan's fingernails, which could have indicated a dispute prior to death, but noted that it also could have been washed away by the sea current if it was present.

[42] He agreed that it was difficult to determine the manner of death due to the body's decomposition, but pointed out that the volume of fluids found in Chan's lungs was much less and unusually uneven compared to typical cases of drowning.

[33] They recommended that the Department of Health should conduct a diatom test in cases where the cause of death could not be determined due to decomposition of a body.

[33] Magistrate Ko Wai-hung ruled out suicide and homicide as possible causes for Chan's death due to insufficient evidence to support this.

[20] In the self-penned Cantonese composition "Explicit Comment" (人話) released in late 2019, singer-songwriter Charmaine Fong made reference to the public's scepticism of the official narrative of Chan's death with the lyric "The truth has long since disappeared; write your ridiculous plots".