In post-conviction proceedings, showing that a trial was defective is not enough. The petitioner must prove that the defect was harmful—that it had a substantial and injurious effect or influence in determining the jury’s verdict. Even for constitutional violations, the Supreme Court has made clear that reversal is not automatic. Instead, the petitioner bears the burden to demonstrate that, but for the error, there is a reasonable probability the result would have been different—i.e., that the error undermines confidence in the verdict. See, e.g., Strickland v. Washington, 466 U.S. 668 (1984); Kyles v. Whitley, 514 U.S. 419 (1995).
This burden is heavier than it may sound. A petitioner must do more than identify mistakes, omissions, or irregularities. He must produce affirmative evidence of prejudice: proof that the identified error actually influenced jurors’ reasoning or would likely have altered the verdict if the trial had been conducted correctly. Courts regularly acknowledge errors—even serious ones such as the use of coerced confessions or suppression of exculpatory evidence—but deny relief because the petitioner fails to establish this causal link. Without reliable proof of harm, nearly all post-conviction claims fail.
The empirical record confirms just how rarely petitioners succeed. Fewer than one-half of one percent of non-capital habeas corpus petitions in federal court result in relief. Most state post-conviction petitions meet the same fate. These outcomes do not imply the absence of trial error; they reflect the absence of quantifiable evidence that an error affected the result (see note).
At Fair Trial Analysis, we help litigants substantiate the effect of trial errors and omissions. Our scientific analysis uses structured surveys and statistical modeling to estimate how a representative jury pool would have likely decided the case had the error not occurred. We do not rely on subjective impressions or advocacy. Instead, we measure how the omission or defect interacts with the trial evidence to influence juror decision-making. The resulting analysis provides an objective estimate of harm—evidence that courts can meaningfully weigh when deciding whether an error was harmless or prejudicial.
We cannot guarantee that any particular finding will favor the petitioner or lead to success in court. But we can provide the missing piece that most post-conviction cases lack: credible, empirical proof addressing the very question courts ask—Did the error make a difference?
Without such proof, petitioners almost always lose. With it, they have a genuine opportunity to show that justice requires a new trial.
Note: Nancy J. King and Joseph L. Hoffmann’s Final Technical Report: Habeas Litigation in U.S. District Courts (National Institute of Justice, 2007) (PDF link) analyzed more than 2,300 non-capital habeas cases filed by state prisoners in federal court and found that only 7 of 2,384 cases (0.29%) resulted in relief—approximately 1 in 300. State-level post-conviction relief rates are also very low. Across jurisdictions, the consistent pattern is clear: even when substantial trial errors are alleged, petitioners rarely meet the evidentiary burden of proving that the error was materially prejudicial to the outcome. See Victor E. Flango and Patricia McKenna, Federal Habeas Corpus Review of State Court Convictions, 31 California Western Law Review 237 (1995) (PDF link).