LOS ANGELES — The FBI said in Boston court Monday that Whitey Bulger’s longtime companion was a willing participant in their 16-year bid to avoid arrest.

The hearing focused on whether Catherine Greig should be released from jail, something her attorney has sought.

Greig and Bulger lived for years hiding in plain sight in a Santa Monica, Calif., apartment. Bulger had fled from Boston, wanted in connection with 19 homicides and other charges.

In court, FBI agent Michael Carasza said Greig had used fake IDs card regularly, including to purchase medications for herself and Bulger. According to the Boston Globe, the FBI showed videotape of Greig getting prescriptions at a Santa Monica drugstore.

Authorities are trying to figure out how Bulger — one of the FBI’s 10 most wanted fugitives — was able to live fairly openly in Santa Monica. One key question is whether he got financial help. The FBI found more than $800,000 in cash inside the walls of the apartment.

In an interview with the FBI on a flight from Los Angeles to Boston, Bulger admitted that he “previously stashed money with people he trusted.” But he did not say whether anyone is hiding assets for him now, according to court records.

Cellphones could help explain how Bulger was able to communicate with his associates without his true identity being discovered by those he saw every day.

Bulger also told federal agents he had traveled — sometimes armed and disguised — not only to his hometown but also to Las Vegas, San Diego and Tijuana, Mexico, court papers said.