The latest on the trial of a Baltimore police officer who is charged with manslaughter in the death of Freddie Gray, a 25-year-old black man who was injured in the back of a police transport van (all times local).

9:10 a.m.

A New York artist is putting a moving billboard on the streets of Baltimore to protest excessive police violence.

Michael D'Antuono also unfurled a banner Tuesday outside the courthouse where police officer William Porter is on trial for manslaughter in the death of Freddie Gray.

D'antuono's message: "It stops with cops." He says he's trying to persuade police officers not to let fellow officers get away with sometimes deadly violence against defenseless citizens.

Gray was a 25-year-old black man who died a week after suffering a spinal injury while he was being transported in handcuffs and shackles in the back of a police transport van.

Porter is also black. Prosecutors say his failure to summon medical help or buckle Gray in with a seatbelt amounted to criminal negligence.

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5 a.m.

Prosecutors in the trial of Baltimore Police Officer William Porter, an officer charged in the death of Freddie Gray, are nearing the end of their case.

Porter faces manslaughter, assault, misconduct in office and reckless endangerment charges stemming from Gray's death. Gray died a week after he suffered a critical spinal injury in the back of a police wagon.

Baltimore Circuit Court Judge Barry Williams on Monday denied a defense motion for a mistrial regarding whether Gray had a pre-existing back injury but said defense attorneys could use the documents in question to build their own case.

Prosecutors say Porter is partially responsible for Gray's death for failing the buckle him into a seatbelt, and for not calling a medic when Gray indicated he was injured.

Trial resumes Tuesday.