Jurors have completed their first day of deliberations Monday in the trial of Baltimore police officer William Porter, the first officer to face a jury decision in the death of Freddie Gray.

Prosecutors say Porter is partially responsible for the death because he didn't call for an ambulance when Gray indicated he needed medical aid and because he ignored a departmental policy requiring officers to buckle prisoners in seat belts. Porter told jurors he didn't call a medic because Gray didn't show signs of injury, pain or distress and said only "yes" when Porter offered to take him to the hospital.

Three black men, four black women, two white men and three white women make up the jury. Judge Barry G. Williams told jurors they could stay as late as they would like each day to deliberate.

During closing arguments, prosecutor Janice Bledsoe described the police wagon that carried Gray as his "casket on wheels." She tried to paint the officer as an indifferent cop who denied Gray medical care in the vehicle where he suffered a spinal injury that killed him.

Defense attorney Joe Murtha responded, "Officer Porter is not guilty of any of this... He acted in a reasonable way." He said the prosecution's accusations went too far, adding, "They want you to be emotionally disturbed by the injuries to Freddie Gray. But Officer Porter didn't cause that."

More On This...

In a final statement from prosecutors, Chief Deputy State's Attorney Michael Schatzow cited Porter's claim that he and Gray had a mutual respect. Schatzow asked, "How much respect does he have when he doesn't take the two seconds to put him in the seatbelt?"

Meanwhile, the city of Baltimore, still on edge after riots broke out in April on the day of Gray's funeral, braces for the verdict.

Porter is charged with manslaughter, assault, misconduct in office and reckless endangerment. He and other witnesses testified that it was the responsibility of the wagon driver, Caesar Goodson, to buckle Gray into the seat belt. Goodson faces the most serious charge: second-degree "depraved-heart" murder.

Porter is the first of six officers to go to trial for charges stemming from Gray's injury and death, and it likely will set the tone for the others and for the city's healing. Gray's death prompted protests and rioting in Baltimore, and his name became a rallying cry in the national conversation about the fractured relationship between the police and the public, particularly poor black men, in America's cities.

As the verdict looms in the most high-stakes and high-profile case in the city's recent history, Baltimore officials are taking pre-emptive measures.

Baltimore Police Commissioner Kevin Davis canceled leave for officers through Friday.

"The community has an expectation for us to be prepared for a variety of scenarios," Davis said.

Mayor Stephanie Rawlings-Blake has urged residents to remain calm.

"Whatever the verdict, we need everyone in our city to respect the judicial process," Rawlings-Blake said. "We need everyone visiting our city to respect Baltimore."

Fox News' Jake Gibson and The Associated Press contributed to this report.