In a ruling Thursday, it guides federal judges to weigh conflicts of interest by insurance companies.
Justices rule 7 to 2 that some defendants aren't competent enough to represent themselves.
The US Supreme Court ruled 5 to 4 Thursday that those held in Guantánamo can challenge their detention.
Two high court rulings on Monday will complicate US efforts to prove certain crimes.
In two rulings Tuesday, the justices took an expansive view of civil rights law.
The Supreme Court allows a 2003 law dealing with 'virtual' child porn that some thought was too broad.
Monday's ruling gives a green light to aggressive antifraud efforts often favored by the GOP.
The 7-to-2 ruling is expected to end a de facto moratorium on executions nationwide.
Ruling 6 to 2, the justices say New Jersey has no right to build a liquefied natural gas plant with a Delaware River pier.