"Or do I need to file the schedule C?"

You still have this confused.

Your taxpayer either is an independent contractor, would file a tax form for their business (in this case, Sched C for Sole Proprietorship), and that would result in their business income and any amount subject to Self-employment taxes, which is Medicare and Social Security, is figured out from the Sched C, on the Sched SE. Done.

Or, you think your taxpayer really is supposed to be on payroll as an employee, a direct hire person and that you and that taxpayer are essentially accusing the Employer (your taxpayer's customer, really), of Lying and manipulating, or, at the least, being completely uninformed of Worker Misclassification. If so, you and your taxpayer intend to tell the IRS and turn the employer in for doing it wrong. That is Form 8919.

Don't do what a lawyer tells you, because the Lawyer is not responsible for Tax Filing. You do what applies.

Tell the lawyer, if the taxpayer really was an independent contractor, the lawyer should be pursuing a Law Suit. Because that's what the lawyer does for a living. Not taxes.