The trials of all the Baltimore officers charged in the death of Freddie Gray have been put on hold by Maryland’s highest court, in a delay that could set back the high-profile cases of alleged police brutality for months.

The six officers facing trials over the death of Gray after a spinal injury in the back of a police van were due in court this winter. But after a jury couldn’t reach a decision in the first case, that of officer William Porter, every other trial has been held up over whether Porter can be compelled to testify in each of these other cases without risking self-incrimination.

Prosecutors have appealed rulings on whether Porter must testify, and the Maryland court of appeals said late Thursday that it would hear all the appeals together on 3 March. After the hearing, the court could take months to issue a written decision.

After the jury in Porter’s case came back deadlocked on all counts and his trial was rescheduled for June, judge Barry Williams ruled that the prosecution could force Porter to testify in the trials of Caesar Goodson, the driver of the van in which Gray allegedly sustained his catastrophic injury, and Sgt Alicia White, Porter’s supervisor that day.

Although Williams granted Porter some immunity in exchange, court-watchers called the ruling an unprecedented move because it called into question Porter’s right not to incriminate himself before his own criminal trial. Prosecutors had argued that allowing Porter not to testify would result in “irreparable harm to the people of Maryland by effectively gutting their government’s prosecution”.

Later, prosecutors sought immunity for the three other officers. But Williams denied the prosecution’s request to force Porter to testify against them because he felt it was a stalling tactic and “subterfuge”.

All of these rulings have now been appealed. And Thursday’s announcement means the cases will go straight to the state’s highest court, while the trials remain on hold.

Neither side is at liberty to comment on the case as a result of a gag order imposed by Williams.