Dakar - The International Court of Justice is due to rule on whether Senegal should extradite Chad's former President Hissene Habre to face trial in Belgium.
Mr Habre, 69, denies charges of killing and torturing tens of thousands of his opponents from 1982 until he was ousted from power in 1990.
He has been under house arrest since 2005 in Senegal, where he fled after being deposed.
The Hague court could also rule that he should be tried in Senegal instead.
Senegal has previously refused four extradition requests from Belgium.
The ruling of the UN's highest court will be legally binding.
Dubbed "Africa's Pinochet", Mr Habre was first indicted in Senegal in 2000 - but the country's courts ruled at the time that he could not be tried there.
His alleged victims then filed complaints under Belgium's universal jurisdiction law, which allows the country's judges to prosecute human rights offences committed anywhere in the world.
In 2005, he was charged by Belgium with crimes against humanity and torture.
There have been years of wrangling in Senegal over what to do about Mr Habre.
The government of former President Abdoulaye Wade changed its position on whether to try him several times, at one stage demanding international funding for a trial.