Evidence
Relevance and its limits
Evidence is relevant if it has any tendency to make a material fact more or less probable. Rule 403 excludes relevant evidence whose probative value is substantially outweighed by unfair prejudice, confusion, waste, or delay. Relevant evidence is presumptively admissible; the objection is the exception.
Character and impeachment
Character evidence is inadmissible to prove conduct in civil cases and in the prosecution's case-in-chief, with exceptions for the accused's pertinent trait, the victim's character, and habit. Impeachment by prior inconsistent statement, bias, criminal conviction, and reputation for truthfulness is heavily tested.
Hearsay
Hearsay is an out-of-court statement offered to prove the truth of the matter asserted. Nonhearsay uses - effect on the listener, verbal acts, circumstantial evidence of state of mind - defeat a hearsay objection. Party-opponent statements are nonhearsay under Rule 801(d)(2). Exemptions and exceptions include present sense impression, excited utterance, then-existing condition, business records, and public records.
Confrontation and privileges
The Confrontation Clause bars testimonial hearsay from unavailable declarants unless the defendant had a prior opportunity to cross-examine. Attorney-client, spousal, physician-patient, and work-product protections each carry distinct waiver rules.
Worked example
A witness testifies that the driver said the brakes are shot, offered to show the driver knew of a defect. That is not hearsay - it is offered to prove knowledge, not the truth of the statement.
Rule of thumb: ask what the statement is offered to prove before applying any exception.