District Attorney's Office for the Third Judicial District v. Osborne, 174 L.Ed.2d 38 (U.S. 2009)(5-4)

Where is enough other incromination evidence and an explanation for the DNA result, SCIENCE ALONE CANNOT PROVE A PRISONER INNOCENT.

I guess "science alone" does not prove the world is not flat.  So, if the DNA rules out a suspect, but the eye-witness says otherwise (what are statistics on eye-witness error rates?), "science alone" cannot exonerate.

Actual innocence is still not an established federal right.  Id., at 53. So, if you can prove you are innocent in fact, too bad, maybe.  Perhaps Guy de Maupassant correctly discerned the true motivation of the people who think science alone should not exonerate and that innocence in fact should not get you out of jail:

August 25. I must kill a man! I must!

August 30. It is done. But what a little thing! I had gone for a walk in the forest of Vernes. I was thinking of nothing, literally nothing. See! a child on the road, a little child eating a slice of bread and butter. He stops to see me pass and says, "Good day, Mr. President."

And the thought enters my head: "Shall I kill him?"

I answer: "You are alone, my boy?"

"Yes, sir."

"All alone in the wood?"

"Yes, sir."

The wish to kill him intoxicated me like wine. I approached him quite softly, persuaded that he was going to run away. And suddenly I seized him by the throat. He held my wrists in his little hands, and his body writhed like a feather on the fire. Then he moved no more. I threw the body in the ditch, then some weeds on top of it. I returned home and dined well. What a little thing it was! In the evening I was very gay, light, rejuvenated, and passed the evening at the Prefect's. They found me witty. But I have not seen blood! I am not tranquil.

August 31. The body has been discovered. They are hunting for the assassin. Ah!

September 1. Two tramps have been arrested. Proofs are lacking.

September 2. The parents have been to see me. They wept! Ah!

October 6. Nothing has been discovered. Some strolling vagabond must have done the deed. Ah! If I had seen the blood flow it seems to me I should be tranquil now!

October 10. Yet another. I was walking by the river, after breakfast. And I saw, under a willow, a fisherman asleep. It was noon. A spade, as if expressly put there for me, was standing in a potato-field near by.

I took it. I returned; I raised it like a club, and with one blow of the edge I cleft the fisherman's head. Oh! he bled, this one!--rose-colored blood. It flowed into the water quite gently. And I went away with a grave step. If I had been seen! Ah! I should have made an excellent assassin.

October 25. The affair of the fisherman makes a great noise. His nephew, who fished with him, is charged with the murder.

October 26. The examining magistrate affirms that the nephew is guilty. Everybody in town believes it. Ah! ah!

October 27. The nephew defends himself badly. He had gone to the village to buy bread and cheese, he declares. He swears that his uncle had been killed in his absence! Who would believe him?

October 28. The nephew has all but confessed, so much have they made him lose his head! Ah! Justice!

November 15. There are overwheming proofs against the nephew, who was his uncle's heir. I shall preside at the sessions.

January 25, 1852. To death! to death! to death! I have had him condemned to death! The advocate-general spoke like an angel! Ah! Yet another! I shall go to see him executed!

March 10. It is done. They guillotined him this morning. He died very well! very well! That gave me pleasure! How fine it is to see a man's head cut off!