Altered Evidence

Is it fair for the prosecution in a criminal case to rely upon evidence altered while in possession of the police?

In Todd's case, the prosecution alleged that his knife had been used to stab the victim. But when the police first examined the knife, they found no blood on it. They found no blood in Todd's pockets where he had carried the knife.

They did find a black debris on it--debris, that suggested the knife's use to puncture a tire some 30 feet away from the area where the victim and Brad Orgill were engaged in a violent and bloody fight.

The knife was not shipped to the state crime with the other physical evidence. Some six months later the state crime lab called the El Paso Sheriff asking where the knife was. It had been hiding out in their evidence room. So Officer Jeff Nohr drove it down to the state lab in Pueblo. At this point we'd been dogging the authorities for six months to test the debris on the knife because of its apparent exculpatory value.

Unfortunately, by the time the knife arrived at the lab, the black debris was gone. We were never told of the missing debris, until in desperation, we obtained a court order 13 months after Todd's arrest, for the state to produce the knife for independent testing. Only when it reached the independent forensic lab did we learn that the debris was gone.

What does the state's playing fast and loose with this crucial piece of evidence suggest? Should such altered evidence be acceptable in a court of law? If so, do we open the door for the more general use of trumped up evidence to obtain convictions?