One of six men charged with intentional violence and damage to public property from a September clash on the Kbal Thnal overpass is to serve a year in prison, while five others convicted are to be freed after their sentences were commuted.

A Phnom Penh municipal judge sentenced Nguyen Thydoc to three years in prison, with one year to serve. His co-defendants were sentenced to 25 days in prison, but released on time served.

"[It's a] terrible injustice for the six men who were convicted by Phnom Penh Municipal Court despite a lack of evidence and eye witnesses," Naly Pilorge, director of rights group Licadho – one of two NGOs that provided legal representation for the defendants – said in a text message this morning. "We are just comforted five men will not spend anymore time in prison again and we hope the Appeal Court will reconsider the sentencing and impisonment of … Nguyen Thydoc."

All six defendants were arrested at a roadblock at the Kbal Thnal overpass the night of September 15, when a mixture of commuters and demonstrators attending a three-day protest held by the Cambodia National Rescue Party allegedly threw rocks at police and destroyed property. Police responded by opening fire into the crowd, killing one man and injuring dozens.

During the trial last week, none of the 30 witnesses – all of whom were police – could identify any of the six defendants, nor did any know whether municipal or national police made the arrests.

Thydoc, the one defendant who was denied bail and has remained in prison since his September arrest, testified during the trial that his confession to throwing rocks was coerced by police, saying they repeatedly shocked him with

electric batons while interrogating him.