Final answer:
The social worker should request the services of a professional translator to ensure clear, confidential, and impartial communication with the client who is a victim of domestic violence and does not speak English.
Step-by-step explanation:
In the scenario where a social worker is assigned a client who is believed to be a victim of domestic violence and the client does not speak English, the most appropriate action for the social worker is to request the services of a professional translator. This ensures clear and accurate communication, maintains confidentiality, and avoids any potential conflicts of interest or misunderstandings that might arise if a family member or a nonclinical agency employee were to translate. It also respects the potentially sensitive nature of the information discussed and upholds a professional standard of care, which could be critical in situations involving violence and vulnerable individuals.