Duterte suffering 'significant memory impairment': defence

Former Philippines president Rodrigo Duterte is suffering from major memory loss that means he sometimes forgets his lawyer's name, according to the defence team preparing his case at the International Criminal Court.

The 81-year-old Duterte faces charges of crimes against humanity at the ICC over his so-called "war on drugs" during which thousands were killed, according to prosecutors.

His trial is scheduled to start on November 30, but judges are weighing whether he is mentally fit to be tried and ordered a medical assessment by three experts.

That assessment has not been made public but Duterte's defence and the ICC prosecutor reacted to it in documents dated September 14 but published on the ICC website on Tuesday.

Duterte "suffers from significant memory impairment that prevents him from retaining recent information and reliably accessing memories", the 13-page defence submission said.

This makes it impossible to engage with the case "let alone give proper instructions to his Lead Counsel, whose name he only sometimes remembers", said his chief defence lawyer, Peter Haynes.

Haynes said he was being forced to prepare the case without meaningful input from his client.

The prosecution, in their heavily redacted seven-page submission, concluded Duterte was "capable of meaningfully exercising his procedural and fair trial rights, and that he is fit for trial".

Under ICC rules, proceedings cannot continue if an accused is unable to understand the charges or participate meaningfully in his defence.

Since his arrest and transfer to The Hague, where the court is based, Duterte has been seen only once at an initial appearance via a video link.

He appeared dazed and confused, mumbling to confirm his name and seeming to doze off during proceedings.

His defence team has since applied for him to be absent on health grounds at subsequent hearings.

Presiding judge Joanna Korner has urged him to make an appearance at a pre-trial hearing on Wednesday and no defence application for an exemption has been made public.

This means Duterte could appear in person at the ICC, the first former Asian head of state to do so.