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Bending the Evidence

Science Smhience: Take Our Word for it Instead

[Ed's note: This post at PrawfsBlawg reminded me of one of my old posts, which I wrote when Arizona prosecutors started complaining when juries expected to see physical evidence before throwing someone into a dungeon.]

This story reports on the so-called CSI Effect on Arizona law enforcement. The CSI Effect is shorthand for jurors' newfound belief that in serious cases, the prosecution should present physical evidence. In a robbery case, the police should gather fingerprints. In a murder case, the police should send DNA to a laboratory for analysis. Jurors have learned about forensic evidence from a popular CBS show, CSI: Crime Scene Investigation.

Prosecutors are not pleased.  Sayeth one prosecutor:

Suzanne Cohen, deputy Maricopa County attorney, says jurors "should expect law enforcement to do their job." But, she adds, "Television has put unrealistic expectations on what we can do with technology."

Prosecutors cite this example to butress their case.

Jurors in Maricopa County Superior Court in Mesa this summer acquitted a defendant in a Tempe commercial burglary case. A witness testified about spotting him and another man dragging out a stereo, and police arrested the defendant a few minutes later with burglary tools in his car.

But jurors told prosecutors after the trial that the police "didn't do enough" while investigating the case and needed to find the defendant's fingerprints inside the building.

I wonder what these "burglary tools" were. Did they include latex or leather gloves, lock picks, etc.? Or did a police officer say that items you and I would ordinarily have in our car are burgulary tools? Based on the quote, it's obvious the police did not find the stolen items in the defendant's car. Why shouldn't a jury want more than a bold assertion that a screwdriver is a "burglary tool"?

Another example.

A Tempe convenience-store clerk identified an accused armed robber who used a pellet gun in the robbery last year. A second witness saw the suspect run out the store.

Jurors could not reach a verdict, telling prosecutors after the trial that police should have tested a soda bottle the defendant left on the store counter for DNA.

Eyewitness identification is the most unreliable evidence. Mistaken ID's are the single greatest causes of wrongful convictions. Yet prosecutors are angry because a jury wants reliable evidence in addition to an eyewitness ID. I can't fault a jury for wanting reliable evidence before sending a man to prison. But I am old-fashioned.

Phoenix police officers approached a group of people standing in an empty lot two years ago and said they saw a man drop a plastic bag containing illegal drugs. Latent fingerprints were never submitted because two officers said they saw the man ditch the drugs and prosecutors thought that was sufficient. Jurors disagreed, acquitting the defendant. They later told prosecutors they wanted the prints.

Ah, the famous dropsy testimony.  Maybe the police didn't test for the defendant's prints because they might not be there.

Thousands of people are wrongly in prison based on eyewitness ID's, "circumstantial evidence," and fabricated police testimony.  Hundreds have been freed after physical evidence has proven they could not have committed the crimes.

If a prosecutors first duty is - as they so often tell juries - to do justice, then shouldn't they ensure that physical evidence, when available, is gathered and tested? What does it tell us about prosecutors when they get angry at jurors who demand that readily available physical evidence be tested?