Last week, at the tail end of a monthlong trial in a federal court in Boston, a tall and impeccably dressed man took the witness stand. Jean Leonard Teganya, a Rwandan, raised his hand and took an oath to tell the truth.

For the next three hours, Teganya's lawyer probed where he was and what he did during the genocide that engulfed Rwanda 25 years ago. More than 800,000 people were slaughtered over the course of about three months.

I sat on a wooden bench in the spectator section on the other side of the courtroom and studied Teganya. Next to me was his uncle, Greg Meyer, who had cold-called me a few days earlier to tell me about the trial. Prosecutors alleged that Teganya had taken part in rapes and killings during the 1994 genocide.Teganya was arrested in 2017 and charged with fraud and perjury when he denied carrying out these crimes in an attempt to gain asylum in the United States. Meyer believed Teganya was innocent.

As a journalist, I covered the genocide from its opening days, first crossing into Rwanda four days after the massacres began. It's no exaggeration to say it was a life-changing experience. Week after week, I reported on the atrocities sweeping across the small east-central African nation. People were hacked by machetes or bludgeoned by clubs and left to lie on the roadside, or in the homes or churches where they were seeking shelter. Neither age nor gender mattered — if they were Tutsis or moderate Hutus or members of the Twa, Rwanda's smallest ethnic group, they were targets for Hutu military, the militia known as the Interahamwe and regular civilians.

Witnessing the sheer scale and brutality of the Rwandan genocide bruised my soul, it crushed my inherent faith in the goodness of humanity. It was also dangerous and there were a couple of way-too-close brushes with death.

Now, here I was, 25 years later, looking at one of those believed to be complicit in the atrocities. Teganya is now 48 years old, balding and wearing glasses. Back then, he was a medical student at a university hospital in Butare, the southern Rwanda town where I stopped for the night shortly after entering the country for the first time.

Any defense lawyer will tell you it is risky to put your client on the stand, but Teganya — wearing a well-fitting dark suit, white shirt and striped tie — was composed. He appeared smart and articulate and answered questions succinctly, elaborating only when necessary. Teganya maintained he had been just a hard-working student, helping wounded patients and protecting Tutsis from marauding Hutus. Teganya's father was Hutu, his mother a Tutsi.

I thought Teganya and his lawyer must have carefully rehearsed his testimony. But after three hours, it felt more as though Teganya had been rehearsing for this moment of reckoning for a much longer time — possibly ever since he fled Rwanda into neighboring Democratic Republic of Congo at the end of the genocide.

By the time the prosecution started questioning Teganya — confronting him with conflicting statements he had made — his testimony started to feel a little too smooth. His brisk, fulsome denials of taking part in rapes, in rounding up Tutsis or carrying out killings, started to ring false.

I knew I hadn't sat in on the full trial so I hadn't heard Rwandan witnesses brought in by both prosecution and defense, nor the testimony of U.S. officials experienced at tracking down documentation to fully gauge whether Teganya was guilty. I felt myself starting to get upset, even angry as I sat in that courtroom. I worried how the passage of time — if witnesses' fuzzy memories — would affect the outcome of the trial.

As it turned out, the jury took less than three hours to convict Teganya for making false statements about his role in Rwanda's genocide on his asylum application for the U.S. He is due to be sentenced July 1.

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