Right after they arrive at the island and get into the jeeps, the lawyer has a discussion with John Hammond about the financial and safety concerns of the park's investors (i.e., the lawyer's clients). The lawyers states that, by the end of the weekend, "If they're not convinced, I'm not convinced." This is exactly the opposite of what he meant to say. The lawyer is on the island to witness things and make judgments for his clients, who obviously aren't there. What he meant to say is this: "If I'm not convinced, they're not convinced." The actor simply blew his line, and the filmmakers didn't catch it.