A federal grand jury is scheduled to hear evidence this week into one of Boston's most enduring unsolved criminal cases, the 1990 theft of priceless artwork from the Isabella Stewart Gardner Museum, according to a former employee who worked at the museum at the time.
The former worker said two FBI agents questioned him about his recollection of the theft several days ago and handed him a subpoena to testify before the grand jury in Boston tomorrow.
The agents told him they were gathering facts on the case and were hoping that the grand jury would "shake things up" in the long-stalled investigation, said the former worker, who asked not to be identified.
The agents did say that they were pursuing the possibility that the theft may have been carried out by three individuals - and not two as has long been publicly believed, the former employee said.
On Friday, a spokeswoman for US Attorney Michael J. Sullivan's office declined to comment on the grand jury, stating that the office never confirms or denies the existence of such a session.
A spokeswoman for the Gardner Museum also declined comment.
The former museum employee read portions of the subpoena to the Globe and said it was signed by Brian T. Kelly, a veteran prosecutor in the US attorney's office. Kelly has helped spearhead the federal investigation into and the crackdown of James "Whitey" Bulger's criminal enterprise.
Thirteen pieces of artwork, including three Rembrandts and a Vermeer, were stolen from the museum, which is located in the Fenway, during the early morning of March 18, 1990. According to press reports, two men dressed in Boston police uniforms persuaded the museum's night watchman to allow them access to the museum by contending they had been sent to investigate a disturbance in the museum's outdoor courtyard.
Once inside, the two disguised as police officers tricked the watchman into leaving his desk, which contained the only alarm to the outside world, by telling him he looked like someone on whom they had a default warrant, according to press reports. After he had left his post, the watchman and a second guard, who had been doing rounds at the time, were handcuffed, bound with masking tape, and then tied up in separate spots in the basement of the museum, according to press reports.
For nearly 90 minutes, the thieves made their way through the museum's darkened galleries, ripping paintings from the walls and in some cases cutting masterpieces from their frames.
Among the stolen pieces was the only seascape that Rembrandt ever painted, "Storm on the Sea of Galilee," and "The Concert," by Vermeer, one of the most valuable paintings in the Gardner collection.
Over the years, the crime achieved notoriety as the largest unsolved art theft in world history with the value of the stolen works estimated between $300 million and $500 million.
The theft was vigorously investigated at the outset by the FBI, which assigned more than 40 agents to the case.
Several museum employees, including the two guards, were given lie detector tests, but no hard leads ever developed.
Over the years, hundreds of leads have been pursued by federal authorities but invariably they involved vague tips from well-intentioned individuals or some less well-intentioned ones who were trying to inveigle money from the museum.
The Gardner has had a $5 million reward posted for the return of the artwork in good condition for more than a decade.
Stephen Kurkjian can be reached at kurkjian@globe.com
