A general amnesty was issued by Johnson but Davis was still under indictment. The Supreme Court just let it die without issuing a formal order of dismissal. Why didn’t they want a trial? Because the outcome would have been embarrassing for the federal government and the late disHonest Abe.
No, Davis was indicted for treason in 1865, served two years in prison, released on $100,000 bail paid by prominent northerners.
His federal case came to trial in December 1868, in a district court headed by former Ohio governor and Lincoln Secretary of Treasury, Justice Salmon Chase, then acting as circuit judge, and Chase favored dismissal of the charges.
After preliminary arguments, President Johnson issued a pardon covering Davis, December 25, 1868, following which the court case was dropped.
My opinion is that Davis & other Confederate leaders could have been convicted of treason, with some courts & judges, but not with others.
Seems to me Johnson's pardons worked out best for all.