B: The Supreme Court ruled race-based peremptories are unconstitutional in 1986.
The ruling came in Batson v. Kentucky. The petitioner was a black man indicted in Kentucky on charges of second-degree burglary and receiving stolen goods. The prosecutor in that case used his peremptory challenges to strike four potential jurors who were black, leaving an all-white jury.
A series of decisions since Batson have established that: criminal defense attorneys cannot exercise peremptory challenges in a discriminatory manner -- such as against African-American jurors; and peremptory challenges can't be used in a discriminatory manner against Latinos. Some lower courts have held that peremptory challenges can't be used in a discriminatory way against whites, either.