Hunter Biden's Attorney Mark Geragos Explains Plea, Talks Presidential Pardon

Mark Geragos says he's confident he would have gotten Hunter Biden off scot-free in his tax evasion trial, but President Biden's son didn't want to put his family back in the spotlight ... so he entered a guilty plea.

Hunter's attorney joined us on "TMZ Live" Monday and we pressed him about his risky decision to have Hunter enter an "open plea" ... meaning there was no deal with prosecutors regarding sentencing.

Mark says he was going to win Hunter's case by flipping the government's argument in the Delaware gun trial on its head ... namely, that HB was so addled by drug use he could not have intentionally violated tax codes.

Sounds like a winning argument, so why would Hunter wave the white flag and plead guilty to all 9 tax-related charges without putting up a fight?

We pressed Mark for an answer ... presenting him with the story we broke -- that Biden planned to pardon his son before September, when the guilty verdict was entered.

Our reporting is rock solid ... Biden planned to pardon his son for more than 3 months and Hunter knew his dad would pardon him when he punted on the tax case ... and while Mark's not disputing our story, he's not coming out and saying point blank that's why they chose an open plea.

Mark says he never talked with the White House about a pardon, but admits it was always in the back of his mind.