Absolute immunity takes care of that.
https://www.google.com/#q=prosecutorial+misconduct+absolute+immunity&undefined=undefined
And it doesn't happen that often right?
2011 update
I thought some of you may be interested in these statistics from the Innocence Project, which has now had some 100 death sentences overturned based upon post-conviction evidence. According to their study of the first 70 cases reversed:
•Over 30 of them involved prosecutorial misconduct.
•Over 30 of them involved police misconduct which led to wrongful convictions.
•Approximately 15 of them involved false witness testimony.
•34% of the police misconduct cases involved suppression of exculpatory evidence. 11% involved evidence fabrication.
•37% of the prosecutorial misconduct cases involved suppression of exculpatroy evidence. 25% involved knowing use of false testimony.
http://caught.net/innoc.htm
http://www.deathpenaltyinfo.org/innocence-and-death-penalty
Blackstone's ratio etc.,
The principle is much older than Blackstone's formulation, being closely tied to the presumption of innocence in criminal trials. An early example of the principle appears in the Bible (Genesis 18:23-32),[1][2] as:
Abraham drew near, and said, "Will you consume the righteous with the wicked? What if there are fifty righteous within the city? Will you consume and not spare the place for the fifty righteous who are in it?[3] ... What if ten are found there?" He [The Lord] said, "I will not destroy it for the ten's sake."[4]
The 12th-century legal theorist Maimonides, expounding on this passage as well as Exodus 23:7 ("the innocent and righteous slay thou not") argued that executing an accused criminal on anything less than absolute certainty would progressively lead to convictions merely "according to the judge's caprice. Hence the Exalted One has shut this door" against the use of presumptive evidence, for "it is better and more satisfactory to acquit a thousand guilty persons than to put a single innocent one to death."[1][5][6]
Sir John Fortescue's De Laudibus Legum Angliae (c. 1470) states that "one would much rather that twenty guilty persons should escape the punishment of death, than that one innocent person should be condemned and suffer capitally."
Similarly, on 3 October 1692, while decrying the Salem witch trials, Increase Mather adapted Fortescue's statement and wrote, "It were better that Ten Suspected Witches should escape, than that one Innocent Person should be Condemned."[7]
Blackstone's Commentaries[edit]
While compiling his highly influential set of books on English common law, William Blackstone expressed the famous ratio this way:
“ All presumptive evidence of felony should be admitted cautiously; for the law holds it better that ten guilty persons escape, than that one innocent party suffer.[8] ”
This variation was absorbed by the British legal system, becoming a maxim by the early 19th century.[9] It was also absorbed into American common law, cited repeatedly by that country's Founding Fathers, later becoming a standard drilled into law students all the way into the 21st century.[10]
http://en.wikipedia.org/wiki/Blackstone's_formulation
