Today, the Connecticut Supreme Court overturned the murder conviction of Donald Raynor because the trial judge denied the defendant's motion for a hearing pursuant to State v. Porter, 241 Conn. 57 (1997). Porter follows Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993), in holding that testimony based on scientific evidence is subject to a multiple factor test to determine its reliability. A Porter hearing is thus a judicial determination on the reliability of the scientific evidence outside the presence of a jury. The Porter hearing is designed to ensure the jury's fact-finding isn't corrupted by bad science.
The defense argued that two reports from the National Academy of Sciences (NAS) have cast doubt on the reliability of firearm and toolmark evidence. Such evidence attempts to ascertain whether a particular gun fired a bullet. The NAS reports suggest more uncertainty in ballistics evidence than police shows and testifying experts would have you believe. So a Porter hearing was necessary to make sure the ballistics' expert testified with the appropriate caveats. However, the trial judge found firearm and toolmark testimony sufficiently reliable without a Porter hearing. The ballistics' expert then testified Raynor's weapon fired the bullets that killed the victim. And the jury convicted Raynor of murder.
The CT Supreme Court found the NAS reports show firearm and toolmark evidence is not an immutable scientific fact, and judges must engage in Porter hearings before allowing the testimony. Such hearings would not necessarily bar the use of ballistic testimony, but ensure the relevant testimony doesn't overstate the known facts. Considering the expert's testimony in Raynor's case was the only objective testimony linking the defendant to the murder, the Court found prejudice and ordered a new trial.
What kind of testimony would be permissible at the rehearing? What can the ballistics expert say about how certain he is Raynor's gun killed the victim? The Court would not say, saying this issue is still too new in Connecticut. Although it pointed to what other Courts have done. So it looks like the trial judge will have to craft an instruction to the jury based on the best available science, and ensure the ballistics' expert doesn't overstate his conclusions. A messy result to be sure. But this is an uncertain world where truth isn't as easily obtainable as it is on TV.