There is "a sword of Damocles hanging over his head," said Dershowitz, who appeared on a "This Week" panel of lawyers discussing the implications of the April 9 raids during which investigators seized Cohen's electronic devices.
“After those raids, how serious is the threat to Cohen and Trump?” Stephanopoulos asked Dershowitz.
“Oh, it’s a very serious threat,” Dershowitz said. “They have enormous abilities to really put pressure" on a witness.
But the law professor also said he's not sure whether Cohen will "flip" to become a prosecution witness who could possibly give some kind of evidence against his client, Trump.
"I think it's very hard not to flip when they’re threatening you with long imprisonment, but I don’t think we know enough," Dershowitz said.
Another panelist, former federal prosecutor Mimi Rocah, disagreed with Dershowitz. Rocah, now a criminal justice fellow at Pace University Law School, said she believes Cohen will cooperate with prosecutors because he's vulnerable.
“I think he flips because I think he committed a lot of crimes, and he has got a lot of jail time that he's facing for that reason,” Rocah said
Dershowitz said Trump has "a unique weapon" on his side in any investigation -- the presidential pardon. However, he said in regard to Cohen, "I don't think he's going to be pardoned."
But ABC News chief legal analyst Dan Abrams, who was also part of the panel, had a different take.
“I think he's going to be pardoned," Abrams said. "I think he feels confident about that.”
After the April 9 raids by the U.S. Attorney’s Office in New York, Cohen and Trump’s attorneys argued that many of the items seized fall under attorney-client privilege and therefore should not be viewed by prosecutors until they, or a neutral third party, have an opportunity to review them.