By Aaron Ross

DAKAR (Reuters) -About 50 people were sentenced to death, many in absentia, in Democratic Republic of Congo on Saturday in connection with the murders of U.N. experts Zaida Catalan and Michael Sharp (OTC:) in 2017, a defence lawyer in the case said.

A local immigration official was among those given death sentences while an army colonel was given 10 years in prison, said Tresor Kabangu, who represented several defendants in the trial. Congo has observed a moratorium on the death penalty since 2003 so those convicted will serve life sentences.

Human rights groups say investigators have ignored the potential involvement of higher-level officials, and Catalan and Sharp’s families said they did not believe the ultimate masterminds had been brought to justice.

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.

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, Kabangu 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, Kabangu said.

A number of the defendants were convicted in absentia because they were either never apprehended or escaped from custody.

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.”

Congo’s chief military prosecutor was not immediately available for comment. Prosecutors have previously said that they followed the available evidence.

Sweden’s foreign minister, Ann Linde (NYSE:), urged Congolese authorities to cooperate with a U.N. mechanism involved in the investigation to shine further light on the matter.

“Crucial that investigation concerning others involved continues to further uncover truth and bring justice,” she said on Twitter (NYSE:).