Italian national Stefano Brizzi, 50, died at Belmarsh high-security prison in south-east London, on 5 February.
When he was jailed last year for murdering Gordon Semple, he was being monitored for mental health issues.
He was taken off the list on 28 December, a pre-inquest review heard.
Days later on 4 January, "suicide watch ceased", senior coroner Dr Andrew Harris told Southwark Coroner's Court.
A noose and a letter "indicating he was thinking about death" was found in a cell he occupied on his own, the hearing was told.
The noose was said to have been discovered on 6 December while he was still on suicide watch. It was not clear whether the letter was found on 10 December or was dated 10 December and discovered later, the court heard.
Dr Harris queried the potential "non-disclosure" of the letter to healthcare staff. He also said there was a suggestion Brizzi made the noose as a result of being bored.
He gave the cause of death as hanging, adding there were no injuries "implying altercation with another party".
The Italian national was serving a minimum of 24 years in prison after he was found guilty in December for murdering PC Semple who was from Greenhithe in Kent.
He had strangled him during a bondage session and then cooked and tried to eat him.
A full inquest, which will take place on 23 April, will seek to determine the "management of information found in his cell indicating he was thinking about death", Dr Harris said.
A man who killed a police officer and then dissolved his body in acid was taken off the suicide watch list a month before he hanged himself, an inquest has heard.