Which of these is NOT a primary responsibility of a private investigator?

Drafting legal documents is not typically a primary responsibility of a private investigator. While private investigators may be involved in gathering information that could support legal processes, the actual drafting of legal documents is generally the role of an attorney. Private investigators usually focus on activities such as conducting surveillance to observe and document behaviors, collecting evidence through various means like interviews and research, and interviewing clients and witnesses to gather relevant information about a case. Their expertise lies in investigative techniques rather than in the legal documentation needed for court proceedings.