Panama’s former strongman Manuel Noriega will face trial for the 1970 disappearance of a leftist union activist, his lawyer said Monday, the latest in a string of cases against the jailed ex-leader.

Noriega, who has served prison terms in three countries since his ouster in a US invasion in 1989, will go on trial on May 21 for the disappearance of Heliodoro Portugal, said his lawyer Ezra Angel.

The former strongman is currently serving a 60-year sentence for the disappearance and killing of his opponents during his time in power, which began in 1983.

Noriega was head of the National Guard and then-de facto-dictator Omar Torrijos’s right-hand man, at the time Portugal was detained by the military in May 1970.

The union activist’s body was found in 1999 outside an old military barracks near the Panama City international airport.

Other military officers are also implicated in the case, Angel said.

Noriega, now 80 years old, is currently in prison in El Renacer penitentiary along the Panama Canal.

After his ouster, he was jailed for 20 years in the United States for drug trafficking, then extradited to France and jailed there two years for money laundering.

France extradited him back to Panama in 2011. He has repeatedly asked to be transferred to house arrest because of failing health, but authorities have refused.

A truth commission in Panama found 110 cases of murders and disappearances of Noriega opponents during his dictatorship.