About 50 people were sentenced to death in Democratic Republic of Congo on Saturday in connection with the murders of U.N. experts Zaida Catalan and Michael Sharp in 2017, a human rights group tracking the trial said.

A local immigration official was among those given death sentences while an army colonel was given 10 years in prison, said Thomas Fessy, Human Rights Watch's senior researcher on Congo. Congo has observed a moratorium on the death penalty since 2003 so those convicted will serve life sentences.

But Fessy and Catalan's sister said investigators had ignored the potential involvement of higher-level officials and the trial had not revealed the truth.

Catalan, a Swede, and Sharp, an American, were investigating violence between government forces and a militia in the central Kasai region in March 2017 when they were stopped along the road by armed men, marched into a field and executed.

Five year trial

Congolese officials have blamed the killings on the Kamuina Nsapu militia. They initially denied any state agents were involved but later arrested the colonel and several other officials who they said were working with the rebels.

After a nearly five-year trial marked by repeated delays and the deaths of several defendants in custody, a military court in the city of Kananga delivered its verdict on Saturday.

Among those sentenced to death was Thomas Nkashama, a local immigration official who met with Catalan and Sharp the day before their fatal mission, Fessy told Reuters. Others were alleged members of the militia.

Colonel Jean de Dieu Mambweni, who also met with Catalan and Sharp before their mission, was sentenced to 10 years, Fessy said.

Prosecutors and defense lawyers in the case were not immediately available for comment.

Sister urges more questions

Catalan's sister, Elisabeth Morseby, said after the verdict that testimony in the case was of dubious reliability given how much time the defendants had spent together in prison and said the conviction of Mambweni was a smokescreen.

"In order for the truth to emerge, all suspects, including those higher up in the hierarchy, need to be questioned, which has not yet been done," she told Reuters.

Sharp's mother, Michele, said she was glad some perpetrators were being held accountable, but wondered who gave the orders.

"Surely someone in the upper echelons of power," she said. "We await further developments."

Prosecutors say they have followed the available evidence.

Fessy said there were still more questions than answers after the verdict.

"The investigation and ultimately this trial have failed to uncover the full truth about what happened. Congolese authorities, with U.N. support, should now investigate the critical role that senior officials may have played in the murders," he said.

Ann Linde, Sweden's foreign minister, echoed that call on Twitter: "Crucial that investigation concerning others involved continues to further uncover truth and bring justice. We encourage authorities to fully cooperate with the UN mechanism."