Yes they can!
“… (L)awyer trust accounts enjoy no special status with regard to garnishment law. Funds in a lawyer trust account are, by definition, client funds and are subject to claims of the client’s creditors.”
For a discussion of this topic, see Sylvia Stevens, Trust Account Lessons: Cautionary Notes (July 2008). Contact Oregon State Bar General Counsel for a more detailed predecessor article from 1998 by George Riemer.