Cuyahoga County Prosecutor Timothy McGinty, saying evidence still needs to be gathered, is expected to present the case to a grand jury, which will determine whether charges will be filed against the officer and his partner.
"We are concerned, we are upset, we are frustrated, we are angry, because we feel that justice is not in process and not in motion in this case," Rice family attorney Jonathan Abady said Friday outside Cleveland's Justice Center Complex.
Rice's mother, Samaria Rice, said she was disappointed with McGinty's handling of the case.
"I am praying the public continues to ask questions to seek the truth," she said at the news conference.
The attorneys sent a letter to McGinty hours earlier, asking him to appoint a special prosecutor.
Authorities say Tamir Rice was killed by Timothy Loehmann, an officer in training, outside a Cleveland recreation center in November 2014 after the boy walked around with a pellet gun that resembled a handgun.
The shooting, captured on surveillance video, sparked controversy given Tamir's age and the true nature of the gun. It also came as the nation reeled from police-involved shootings
of unarmed African-American men; Tamir was black.
A grand jury will decide whether Loehmann and his partner, Frank Garmback, will face charges.
McGinty not backing down
McGinty responded to Tamir's family Friday with a news release that made no indication he would step aside, but defended the release of the expert reports.
The two reports, as well as a third one by the Highway Patrol that came to no conclusion, were posted on the prosecutor's website on the night of October 10.
"Whatever the outcome of a case, the public should not be surprised by -- or unaware of the basis for -- any decision," McGinty's Friday statement reads. "Some parties may be displeased with evidence or reports as they are disclosed, but by making them public before conclusion, there is an opportunity to correct errors."
McGinty previously has said his office wasn't using the reports to reach a conclusion and the grand jury will get to consider all the evidence once the investigation into shooting is done.
Rice attorneys: McGinty's explanation disingenuous
But Rice family attorney Subodh Chandra said Friday that McGinty's claim was disingenuous. Prosecutors often don't just dump evidence in front of grand juries, but rather they recommend that a grand jury makes a decision in a particular way, he said.
The release of the expert reports tips McGinty's hand and risks influencing the grand jury pool before they take the case, Chandra said.
"Prosecutors don't throw up their hands and say, 'Gee, I don't know,' " Chandra said at the news conference.
Rice attorneys say the reports that conclude the shooting was reasonable -- by a Colorado prosecutor and a former FBI agent -- resort to speculation about what the officers might have seen or thought. Neither writer interviewed the officers, they said.
"The unorthodox, if not unprecedented, use of expert reports at this stage of the criminal proceeding is all the more troubling because these reports are clearly designed to exculpate the officers," the Rice attorneys wrote in their letter to McGinty. "Typically, biased reports of this type are offered by criminal defense lawyers at trial.
"Here, it appears your office has abandoned its obligation to diligently pursue criminal charges against the killer of a 12-year-old boy because the shooter was a police officer. We view this as an abuse of the grand jury process. Regrettably, under these circumstances, we fear the grand jury is being utilized to cover up an improper effort to protect police officers who should be subject to the criminal law."
Tamir had been standing near the swings of a recreation center near his home on November 22, holding the pellet gun, police said.
Someone called 911, reporting there was "a guy with a pistol," adding that the weapon was "probably" fake.
Information that the gun the caller saw was probably not real and that the person holding it appeared to be a juvenile was not conveyed to Loehmann and Garmback when they were asked to investigate, according to recordings that law enforcement released.
Video of the incident shows a patrol car pull up on the snowy grass near a gazebo where Tamir is standing. Within two seconds of exiting the police car, Loehmann shoots the boy.
The gun was in the waistband of Tamir's pants. S. Lamar Sims, the senior chief deputy district attorney in Denver who authored one of the expert reports, wrote that the video appears to show the boy's hands moving toward his waistband, but that whether he reached for the gun is unclear.
Tamir died a day after he was shot.
Cleveland police initially were investigating the shooting, but amid calls for an independent investigation, the Cuyahoga County Sheriff's Office took over the probe.
In June, McGinty released the sheriff's office report. Also that month -- in a non-binding review of the case -- a Cleveland judge found probable cause for the charges of murder, involuntary manslaughter, reckless homicide, negligent homicide and dereliction of duty against Loehmann.
Besides taking issue with the expert reports, the Rice family attorneys say it has taken too long to take the case to a grand jury.
"While we understand the general need to proceed with caution and thoroughness, no reasonable prosecutorial effort should be taking this long, especially under the circumstances of this case," the lawyers' eight-page letter to McGinty says.
In the letter, the attorneys note two fatal police shootings in Baltimore and North Charleston, South Carolina, over the last year have already gone to grand juries.