Updated from 2:48 p.m. ESTEven if Kenneth Lay is compelled by subpoena to go before the Senate Commerce Committee, there's a good chance the former Enron chief executive won't say anything, legal experts said. Lay cancelled his voluntary testimony Monday before the Commerce Committee, citing an "increasingly prosecutorial" tone on the part of lawmakers. If, as the committee has vowed, Lay is subpoenaed on Tuesday, he is only legally obligated to appear. If he doesn't want to speak, he can invoke his Fifth Amendment rights. It is unlikely the former Enron executive is actually going to talk, legal experts said. "If he faces a subsequent lawsuit -- criminal or civil -- anything he says can be used against him," said Michael Perino, a professor of law at St. John's University, who expects Lay will take the Fifth. Lay's decision to call off his appearance in Washington came a little more than a day after the release of a report by a committee of Enron's board of directors, the "Powers report," which criticized Lay specifically. The only way Lay would be forced to answer lawmakers' questions is if they gave him immunity, or freedom from any further prosecution based on what he said before them in Congress. "They are unlikely to give immunity, because it would make subsequent prosecution difficult," said Perino. "I don't think that they would want to do that at this point." Currently, the Justice Department is looking into whether or not there is a criminal case to be made against Enron, and it would be opposed to giving Lay immunity at this point. "Given the seriousness of the situation, I don't think they'd give him immunity," said Bill Allison, managing editor of the Center for Public Integrity, a nonpartisan watchdog of government ethics. Jeff Skilling, another former chief executive officer of Enron, still plans to testify before Congress on Thursday and not exercise his Fifth Amendment right, press reports said today.