Former State Department IT expert Bryan Pagliano has refused to answer deposition questions about his work on Hillary Clinton’s private email server, keeping its operations hidden and increasing the chances that Clinton herself must testify in the case—though observers said it is still a longshot the Democratic presidential hopeful will be called to the stand.

The issue is part of a civil lawsuit by Judicial Watch, a conservative watchdog group, which aims to determine whether Clinton and her top staffers violated the Freedom of Information Act (FOIA) through her use of a personal email address and private server at her New York home. Pagliano’s lawyers have said he’ll remain silent during his upcoming but as yet unscheduled deposition.

Unlike in a criminal case, judges in civil cases can draw inferences about the guilt of someone who decides to plead their Fifth Amendment rights.

Pagliano had previously asserted his Fifth Amendment rights before the House Select Committee on Benghazi and reportedly had been granted immunity as part of the FBI’s investigation of possible mishandling of classified information related to the server. Lawyers speculated that having him speak in the civil suit could endanger the immunity arrangement, expose him to new legal risk, or potentially impede his future employment.

"Your chief concerns as counsel is to make sure you do everything you can to protect your client where the stakes are highest," added Henry Hockeimer, a former federal prosecutor now at Ballard
Spahr. "In this case, it’s the criminal investigation."