This week, prosecutors in Chicago, Connecticut, and Alabama tried or charged defendants who committed their alleged crimes years, or sometime decades, earlier. Many of the witnesses in these cases never told police or prosecutors what they knew before now. Can these witnesses be charged with obstructing justice or withholding evidence?
No. To be prosecuted for obstruction of justice or withholding evidence, someone with knowledge of a crime must lie to a police officer, either by fabricating or withholding information. In the Connecticut and Alabama cases, the witnesses were not questioned by police at the time of the murders and thus had no opportunity to lie.
In the Chicago case, one of the witnesses did lie to police: She backed up the alibi of one of the alleged killers when questioned nine years before. But since Illinois' statute of limitations for obstruction of justice is three years from the date of the offense, she can't be charged, either.
In Illinois and most other states, it's not a crime to fail to report what you know about a crime; the law doesn't compel you to come forward and report a murder. Similarly, state statutes also require an affirmative act to label someone an accessory after the fact. You can't be called an accessory just for keeping silent.
Finally, in all three cases, the prosecution relied heavily on these witnesses' testimony. So, even if the witnesses could be charged, it wouldn't make strategic sense for prosecutors to threaten them with punishment. Not if they want to nail the defendants.