The trials were welcomed at the time but there were concerns about justice being seen to be done, as proceedings took place behind closed doors with media and the public banned.
What information has emerged has come from government statements, although reporters were briefly allowed to observe proceedings in February.
HRW’s Anietie Ewang said: “Nigeria needs to pursue justice for those responsible for Boko Haram’s atrocities and end the prolonged detention of thousands of suspects.
“However, to achieve justice and deter extremist attacks, the Nigerian government’s overall strategy and trial procedures need to conform with constitutional safeguards and international standards.”
Ewang said the group was able to monitor the third round of proceedings in July, at which more than 200 defendants were tried.
A total of 113 people were convicted and sentenced on charges including membership of a proscribed organisation, supporting Boko Haram and participating in acts of terrorism.
One of those found guilty was sentenced to 20 years in prison for his part in the mass kidnapping of more than 200 schoolgirls from the northeastern town of Chibok in 2014.