Prosecutors have said they intend to call Porter as a witness against at least two other officers, including the van driver and sergeant who checked on Gray after he was put inside the van.
The judge ruled earlier this month that each officer will get his or her own trial and that they will be held in the city. Five of the six officers appeared in court Tuesday for the first time in their case. Only Porter did not attend.
Gray's death led to protests and rioting in Baltimore, and became a symbol for the treatment of black men by police in America. It also shed light on long-standing and systemic disenfranchisement of African-Americans in the city.
Attorneys for the six officers asked Williams to move the trials outside of Baltimore, citing pre-trial media coverage they say could prejudice a jury. The judge rejected their request earlier this month, but kept the door open to re-evaluate his decision should the state and defense run into problems seating a jury.
Prosecutors suggested in a letter to the judge that the state intends to call Porter to testify against Sgt. Alicia White, who faces the same charges he does, and Officer Caesar Goodson, who faces an additional "depraved-heart" murder charge.
Goodson, the van driver, will be tried Jan. 6 and White's trial will begin Jan. 25.
Officers Garrett Miller and Edward Nero face misdemeanor assault, misconduct in office and reckless endangerment charges, as does Lt. Brian Rice, who also faces a manslaughter charge. Their trials will be held in February and March.
Prosecutors asked that Miller and Nero be tried before Rice, suggesting that they could call the officers to testify against each other.
It isn't clear what the officers will say in their testimonies or how the state plans to use them as witnesses.
Officers arrested Gray on April 12 in West Baltimore after he ran from officers. Police say he was carrying an illegal switchblade; prosecutors have said the knife was legal.
Gray was not restrained with a seatbelt inside the transport van, although policy called for officers to belt him in. Roughly 45 minutes after his arrest, Gray arrived at the Western District stationhouse, where he was unresponsive.
Although each officer will get his or her own trial, the order in which the officers will be tried is significant. Porter, Goodson and White were primarily involved in Gray's transport. According to charging documents, they failed to render aid to Gray once he'd been placed into the police transport van.
The van made several stops during which White, Porter and Goodson checked on Gray, but did not call a medic, according to charging documents.
Miller, Nero and Rice were the officers who had initial contact with Gray, spotting him near the Gilmor Homes, chasing him and ultimately putting him in handcuffs and leg restraints before placing him inside the transport van.
The Associated Press