Officer Peter Liang enters Brooklyn Supreme Court on Feb. 11, 2015 to be arraigned for shooting Akai Gurley to death. View Full Caption DNAinfo/Rachel Holliday Smith

BROOKLYN — The police officer accused of shooting unarmed Akai Gurley in a Brooklyn hallway is complaining that prosecutors have an “undeniable bias” against the NYPD.

The accusation is contained in a 44-page document filed by Officer Peter Liang’s lawyers that blasted the Brooklyn District Attorney's office for indicting Liang in the death, which they say was an “accident,” while declining to present evidence to a grand jury when a retired correction officer shot and killed an unarmed straphanger during a dispute in a downtown Brooklyn subway station last March.

“It is hard — if not impossible — to reconcile the District Attorney’s prosecution for (Liang’s) accidental shooting with the decision of that same office not to prosecute, or even present to a grand jury, the fatal shooting of 32-year-old construction worker Gilbert Drogheo (last March) by retired corrections officer, William Groomes,” the lawyers wrote in a memorandum asking a Brooklyn judge to dismiss Liang’s indictment.

But a spokesman for Thompson, whose mother is a retired NYPD officer, insisted "there is no comparison to the Groomes case, which involved a struggle over a gun — it was a completely different kind of (weapon) discharge. To suggest this case has a similar set of facts is preposterous."

Liang, 27, was on a patrol in an East New York housing project last November with his partner when he entered a darkened stairwell with his service weapon drawn. The rookie was holding a flashlight in one hand and his Glock 9mm in the other when the weapon fired. The bullet ricocheted off a wall, hitting Gurley in the chest on a landing below.

Liang was indicted on second-degree manslaughter, reckless endangerment, second-degree assault and official misconduct charges last February — primarily because prosecutors insisted he needlessly had his finger on the trigger in an apparent violation of NYPD guidelines.

While Thompson acknowledged that Liang did not intend to kill Gurley, 28, and a father of a young daughter, he “had his finger on the trigger, and he fired the gun.”

But Groomes was spared a grand jury inquiry even though he got into a heated argument with Drogheo in a subway car, then followed him off the train to a mezzanine level, where he got into a struggle and his Glock went off, killing Drogheo.

Thompson said criminal charges were not warranted because he could not prove whether the shot was intentional.

Liang's lawyers insisted, however, “whether or not Groomes intentionally shot and killed Drogheo, Groomes must have had his finger on the trigger during the dispute before the gun went off.”

They claimed Liang "is being prosecuted in bad faith by virtue of an undeniable bias against police officers with the NYPD."

But the DA said Groomes' victim went for his weapon.

"To say this office has a bias against police officers is absurd," a DA spokesperson said. "We work side by side with the NYPD every day and have nothing but respect for all of the officers."

Liang is due back in court Tuesday when a judge may announce his decision on whether to dismiss the charges against him.

Liang's legal team also assailed the underpinnings of the case as “nonsensical and disingenuous.”

Without admitting Liang had his finger on the trigger, Liang attorney Stephen Worth maintained that the officer's actions were not in violation of the NYPD’s guidelines, which he insisted are not hard-and-fast rules.

“There are times when an officer should (or at least can) have his or her finger at the trigger, and such a time would be when an officer is in a patently dangerous situation, like when conducting a nighttime vertical patrol in a pitch-black stairwell,” Worth said.

The lawyers also challenged a disturbing allegation that Liang waited four minutes before calling for help after shooting Gurley. They say they have eyewitnesses who saw Liang collapse to the floor after he radioed for help.

Thompson's spokesman said his office's documents are presently under seal, but when they are released they will reveal the "fallacy of (Worth's) outrageous" allegations.