Responding to the lawsuits for the first time, lawyers from the state attorney general's office who are representing Mosby said in filings late Friday that she can't be sued for actions taken as a prosecutor.
They also noted that the probable cause to file the charges against the five officers was validated by a District Court commissioner, a grand jury and the judge who oversaw the cases.
"It is undisputed that other persons and entities within the criminal justice system repeatedly found probable cause after the filing of the" charges, her attorneys wrote.
Mosby's office filed charges against six officers involved in Gray's April 2015 arrest. Prosecutors said three of the officers wrongly arrested Gray and that all failed to follow Police Department rules that required officers to secure him with a seat belt in a police van and to seek medical care for his injuries.
The first trial ended in a mistrial when jurors failed to reach a verdict, and the next three officers were acquitted by a judge. After the third acquittal, prosecutors dropped all remaining charges against all officers.
The lawsuits, filed while the criminal cases were ongoing, were brought by Officers Garrett Miller, Edward Nero and William Porter, Sgt. Alicia White and Lt. Brian Rice. Officer Caesar Goodson, the driver of the van inside which Gray was injured, has not joined the lawsuits.
The officers allege that Mosby and Sheriff Samuel Cogen knowingly filed false charges against them "in furtherance of [their] own personal interests and political agenda."
"Their illegal arrests were made without probable cause and demonstrated ill will, improper motivation and/or evil purpose," attorney Joseph Thomas Mallon Jr. wrote in the suit filed by Miller and Nero.
Mosby's attorneys are asking U.S. District Judge Marvin J. Garbis to throw out the lawsuit or rule in favor of Mosby.
The officers also claim defamation. Their attorneys have cited Mosby's announcement of the charges against the officers, in a speech on the steps of the War Memorial building in downtown Baltimore, days after rioting that led to a citywide curfew.
Critics have attacked Mosby for addressing protesters during her remarks, and using her campaign slogan, "Our time is now."
Mosby's attorneys say the majority of her speech was reading word-for-word from the charging documents filed against the officers earlier that day, and noted that she prefaced her remarks by saying the officers were presumed innocent until proven guilty.
"The State's Attorney concluded her prepared statements with an expression of 'hope' that 'everyone will respect due process' and act peacefully," her attorneys wrote.
They said Mosby made no false statements of fact, and supported her legal opinion by reading from a legal document. They added that the officers were public officials, which gives them a heightened burden for proving defamation.
The officers alleged that Mosby "knew ... that no probable cause existed that either Miller or Nero had committed any crime."
Mosby's attorneys said the officers offer no proof to back up the claim.
"Given that charges brought against Plaintiffs survived rounds of judicial scrutiny before proceeding to trial, there can be no plausible claim that State's Attorney Mosby had 'serious doubts,' or had 'a 'high degree of awareness of' the charges' 'probable falsity,'" they wrote.
Mosby's attorneys said the officers can't back up their claim that Mosby filed the charges "in furtherance of her own personal interests and political agendas."
But more broadly, they said, prosecutors can't be sued for their actions.
"A prosecutor's decision to move forward with criminal charges ... is exactly the kind of conduct that is absolutely immune from a civil claim for damages in state or federal court," they said. "Consequently, these claims must be dismissed."
City attorneys representing Cogen, of the sheriff's office, have responded to the suit by arguing that Cogen had little actual involvement in the filing of charges other than reviewing materials provided to him by prosecutors. His response raised questions about prosecutors' statements that they had conducted an independent investigation with the help of the sheriff's office.