Officer Edward Nero, one of six Baltimore officers charged in the arrest and death of Freddie Gray, faces assault, misconduct in office and reckless endangerment charges.
Gray's death prompted protests, rioting and looting in Baltimore, and his name became a rallying cry in the growing national conversation about the treatment of black men in America by police officers.
Porter was tried by jury in October, but his proceedings ended in a mistrial after the jurors failed to reach a unanimous decision on any of the four charges he faces.
While video footage taken from both city surveillance cameras as well as cellphone videos shot by bystanders will be admissible, Williams ruled that any audio in which Gray can be heard screaming is considered prejudicial and will be excluded.
