FORT BRAGG, N.C. — U.S. Army prosecutors offered the first details of a rare criminal case against a general, alleging in a military hearing Monday that he committed sex-related crimes involving four female officers and a civilian.

A hearing on evidence in the case against Brig. Gen. Jeffrey Sinclair opened Monday at Fort Bragg, home to the 82nd Airborne Division. Officials said the Article 32 hearing, similar to a grand jury proceeding in civilian court, was expected to last at least two days.

The first witness called was Maj. Gen. James Huggins, the former commander of the 82nd Airborne and Sinclair’s direct superior during his most recent combat tour to Afghanistan.

Huggins recounted that on March 19, a female captain came to his office late at night in tears. She reported that she had been involved in a three-year-long sexual affair with Sinclair, then her direct commander and a married man. Adultery is a crime under the military code of justice.

Huggins said he knew the female officer to be a good soldier whom Sinclair had specifically asked to have transferred under his command.

According to Huggins, the captain said Sinclair had once forced her to perform oral sex on him, but that she also had sex willingly with her boss both at Army bases in the United States and on deployments to Germany, Iraq and at the airborne division’s headquarters in Afghanistan.

When she had tried to end the affair, Sinclair had threatened her and persisted in pushing for sex, according to Huggins’ testimony. But she also told Huggins she finally decided to report Sinclair after finding e-mails exchanged with other women in his account.

“She was exceptionally emotional, fearful,” Huggins recounted Monday. “She stated that she knows this would basically end her career.”

After the conversation, Huggins initiated a criminal investigation of his deputy commander, whom he described as a personal friend.

Sinclair now faces possible courts martial on charges including forcible sodomy, wrongful sexual conduct, violating orders, engaging in inappropriate relationships, misusing a government travel charge card, and possessing pornography and alcohol while deployed.

Sinclair sat silently at the defense table during the hearing, rarely making eye contact with Huggins as he testified. Sinclair had served as deputy commander in charge of logistics and support for the division’s troops in Afghanistan from July 2010 until he was sent home in May because of the allegations.

There have been only two other court-martial cases against Army generals in recent years.

Until Monday, the Army had kept secret all details of the allegations against Sinclair, refusing to release charging documents filed against him in September. That secrecy is different from other high-profile case where Army prosecutors were quick to release charging documents.

In March, the Army quickly released charge sheets laying out evidence against Staff Sgt. Robert Bales, the soldier accused of gunning down 17 Afghan civilians during a massacre in southern Afghanistan. The first Article 32 hearing in Bale’s case also began Monday across the country in Washington at Joint Base Lewis-McChord, south of Seattle.

Before prosecutors could start presenting their case against Sinclair Monday, defense lawyer Lt. Col. Jackie Thompson alleged that military investigators had violated his client’s rights by reading confidential emails he had exchanged with his lawyers and wife discussing the accusations against him.

Under questioning from Thompson, the lead investigator for the case acknowledged she had read the confidential e-mails, violating the terms of the subpoena used to obtain them from Sinclair’s service provider. Those e-mails were later turned over to prosecutors, who are barred from seeing Sinclair’s communications with his counsel.

Thompson then asked Criminal Investigative Command Special Agent Leona Mansapit if she had the resources she needed to conduct a proper investigation in Sinclair’s case.

“Probably not, sir,” Mansapit replied. “I wish I had.”

The defense is asking the officer conducting the hearing, Maj. Gen. Perry L. Wiggins, to either require all new prosecutors to be assigned or the case thrown out.

“The investigators were tainted, and they tainted the prosecutors,” Thompson told Wiggins. “They bungled the investigation, and if you leave them in place, they will bungle the prosecution as well.”

A visibly flustered lead prosecutor, Lt. Col. William Helixon, was put in the uncomfortable position of calling two of his fellow prosecutors to the witness stand to deny they had read the privileged e-mails. The defense learned of the apparent violation by spotting the e-mails among 16,000 pages of evidence turned over by the prosecution earlier this month.

Wiggins eventually elected to proceed with the Article 32 hearing, after which he will make a recommendation up the chain of command about whether to court martial Sinclair. The hearing was set to resume Tuesday morning with the female captain taking the witness stand.