Constitutional Obligations
Constitution plays limited role on discovery area, since it is usually an informal procedure.
Brady – P cannot suppress evidence favorable to the accused that the D has asked for; violates DP; called “Brady Material”…P must turn over exculpatory evidence where material
Bagley – information withheld to impeach a government witness
held disclosure required only if material to either guilt or punishment and this not material
set aside if reasonable likelihood affected jury (Napue test … low standard)
test for materiality:  reasonable probability had evidence been disclosed to D, result of proceeding would have been different
hung jury concept… no unanimous jury to convict
Very low standard of materiality …. Court remanded for finding.
C says ability to effectively impeach is a very important part of the process
Bagley standard gives no incentive for P to disclose
Look at suppressed evidence collectively, in light of all other evidence (again low standard)
Police
must also communicate relevant information to D
whole entity … even if P did not know, still responsible for police’s failure to disclose
Preservation of Evidence
Don’t have to give D notice testing powder, need not preserve
D can file motion to observe, maybe to test any leftovers, but can’t interfere with normal investigation unless actual bad faith
Timing
disclosure generally best before trial (more efficient)
but can wait until during (judges encourage before)