Which is correct?
- Plaintiff, Jane Doe, individually and as representative of the estate of John Doe, files this complaint . . .
- Plaintiffs, Jane Doe, individually and as representative of the estate of John Doe, file this complaint . . .
I think number 1 is correct.
What we are really asking is whether we have one plaintiff or two, right? Depending on how you answer that question, both 1 and 2 could be correct. You match the verb to the subject:
"Plaintiff . . . files . . ."
"Plaintiffs . . . file . . ."
Here, I believe we have one plaintiff who acts in two capacities. So I think "Plaintiff . . . files . . ." is correct.
Here is some support from Garner's Modern American Usage:
- If a sentence has two or more singular subjects connected by and, use a plural verb. Yet if the subjects really amount to a single person or thing, use a singular verb."
I think what we have in number 1 is what Garner describes in the second sentence of the quotation.