Seven Palestinian murders are still unsolved and their cases unpursued, Human Rights Watch said in a statement on Thursday.
"The Gaza government has apparently not even begun a promised investigation more than four months after gunmen killed seven Palestinian prisoners accused of collaboration with Israel," HRW said.
The seven men in question were arrested last November during Israel's Operation Pillar of Defense, on accusations of being spies for Israel. The men were murdered when armed men broke into their jail cells, where they were serving time for the alleged espionage. Their bodies were dragged through the streets by motorcycles. Hamas's military wing later claimed responsibility, and pinned notes to the men's bodies that said, "Al-Qassam Brigades announces the execution of the traitors," HRW translated.
At the time of the murders, Hamas deputy leader Moussa Abu Marzouk called the killings "unlawful" and said the perpetrators "should be punished and it must not be repeated," Reuters reported. But HRW alleged that no such punishments have been forthcoming.
"Hamas's inability or unwillingness to investigate the brazen murders of seven men makes a mockery of its claims that it's upholding the rule of law in Gaza," said Sarah Leah Whitson, Middle East director for HRW in New York, in a statement.
"Even before the killings, the abuses the men suffered made the criminal justice system a travesty, regardless of their guilt or innocence."
A Hamas spokesman denied HRW's accusations, and claimed that Hamas's prosecutor general had set up an inquiry just after the incident, and the committee had already made recommendations, the BBC reported.
The spokesman also called HRW "unprofessional" for alerting Hamas to HRW's report only a day before the report was published.
HRW put their report out on the last day of a month-long campaign by Hamas that called for collaborators with Israel to step forward in exchange for amnesty, Reuters said. The program ended on Thursday April 11 at midnight.