Justin Slaby thought he had made it. The U.S. Army veteran whose hand had been blown off by a grenade in 2004 passed the basic fitness tests to become an FBI special agent and reported for training at Quantico, prosthetic hand and all.

Slaby’s FBI trainers, though, had other ideas. They concluded that the 30-year-old’s prosthetic hand prevented him from safely firing a gun or properly holding down a suspect during a search. They told him he could not be a special agent — at least not now.

Slaby disagreed and sued.

The case, which is scheduled to go to trial Monday in federal court in Alexandria, has spawned discord in the FBI and spurred an investigation of a supervisory agent accused of putting inappropriate pressure on a witness. It also has put U.S. attorneys in the awkward position of having to argue against a man they describe in court filings as “a disabled veteran whose patriotism and dedication to the nation are not in question.”

“But whether or not he is the victim of intentional disability discrimination at the hands of the FBI,” the attorneys wrote, “is another matter.”

By his attorneys’ account, Slaby, of Stafford County, had wanted to “serve his country” since he was 18 years old. He was deployed to Iraq and Afghanistan, working with an Army ranger regiment, until a defective stun grenade detonated in his left hand in a training accident in 2004.

Working at the FBI was Slaby’s backup plan, according to court filings. He got a business management degree at Upper Iowa University and stayed in shape so he could apply, then successfully passed a fitness-for-duty test. He was told to report to Quantico for training in January 2011, his attorneys wrote.

“He was ecstatic and ready to serve, especially in light of his successful battle to overcome the loss of his hand,” they wrote.

Those at Quantico, though, were apparently not so excited to see him.

Slaby’s attorneys wrote that instructors accused the former solder of being unable to fire a gun with his left hand — even though he had developed a technique to do so, his attorneys argue — and that one instructor reportedly said, “What’s next, guys in wheelchairs?” Eventually, the FBI moved Slaby into a “medical recycle” status — suspending his training until a better prosthetic could be developed, court filings show. He now works for the agency’s Critical Incident Response Group.

At issue is not only whether Slaby can fire with his left hand, but also whether that skill should be required at all. Slaby’s attorneys claim that others with similar injuries have been allowed to remain special agents and that even uninjured agents often cannot fire accurately with their non-dominant hands.

“Under the law and under common sense, weak-hand shooting is not an essential function at the FBI,” said John W. Griffin Jr., one of Slaby’s attorneys. “It’s a situation to be avoided at all costs.”

U.S. attorneys representing the FBI claim in court filings that even if Slaby can pull a pistol’s trigger with his prosthetic hand, he cannot do so safely. They also say that he cannot keep a suspect subdued with one hand and search with the other and that putting him in the field might put other agents at risk.

Slaby sued the FBI last year, asking for back pay and to be allowed to complete his training to become a special agent. As attorneys for both sides have traded barbs, the case has rippled through the FBI from Milwaukee to Washington. Most recently, a federal district court magistrate judge derided as “wholly inappropriate” comments that a Milwaukee supervising agent, Teresa Carlson, made to another agent who had evaluated Slaby before the veteran was hired.

According to court filings, Carlson told the agent, Mark Crider, that he should “come down on the side of” the FBI when he was called to testify in Slaby’s case. Slaby’s attorneys argued that this was akin to the subornation of perjury, although Crider ultimately contradicted the FBI, testifying that it was unnecessary for an agent to be able to shoot with a non-dominant hand.

Court filings show that the Office of the Inspector General has launched an investigation into Carlson’s conversation with Crider. FBI spokesmen said Carlson was temporarily transferred from Milwaukee to an assignment in the D.C. area in late June, but they would not say whether it was because of that probe.

Patricia Sulzbach, Carlson’s attorney, said Carlson “cannot defend herself and provide an accurate account of what actually transpired because of the [inspector general’s] investigation, but said Carlson had “no role” in Slaby’s removal from the academy.

Spokesmen for the FBI and the U.S. attorney’s office declined to comment on Slaby’s case. Griffin said the FBI had not granted a request from Slaby to allow him to talk to reporters.