BOSTON (AP) — A Massachusetts judge has blocked prosecutors’ request for the names of witnesses who cooperated with an internal probe into former state Senate President Stanley Rosenberg and his estranged husband Bryon Hefner.

Superior Court Judge William Sullivan said in Monday’s decision that the witnesses did not come forward willingly in the Senate investigation and spoke to Senate-hired investigators only “after repeated assurances” their names would remain confidential.

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Attorney General Maura Healey’s office sought the records, saying they could lead to more potential victims as it prosecutes Hefner. Her office declined to comment.

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Hefner is facing criminal charges of sexual assault, distributing nude photos without consent and criminal lewdness. He has pleaded not guilty.

Rosenberg, an Amherst Democrat, stepped down in May after 31 years as a lawmaker.

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