House Judiciary Chairman John Conyers (D-Mich.) paid more than $16,500 in the past three months to a Washington, D.C.-based law firm known for advising Members on ethics issues, according to a campaign finance report filed Thursday.

A Conyers spokesman did not immediately return a request for comment, and it is not known why Conyers hired the law firm.

The Michigan lawmaker has previously reported paying nearly $17,500 in fall 2009 to the same law firm, which his office described in February as payments for “routine legal advice.” He has paid the firm about $34,000 in the current election cycle.

On its website, the Brand Law Group describes itself as a specialist in “protecting and defending the rights of witnesses involved in government investigations.”

Conyers reported three payments to the firm since April, with the largest payment for $10,000 made in early June.

Conyers’ wife, former Detroit City Councilwoman Monica Conyers, was sentenced to 37 months in prison in March for her role in a pay-to-play scheme over a $1.2 billion sludge treatment plant contract issued by the city. John Conyers was not implicated in the scandal.