The Prosecuting Poison Pill Dealers Act would amend federal drug laws to expand criminal liability for drug dealers whose substances contribute to someone's death or serious injury. Currently, prosecutors must prove that a controlled substance directly caused a death or injury, but this bill would lower that standard by allowing prosecution if the drug was simply a "substantial factor" in the harm, even if other substances also played a role. This means drug dealers could face criminal charges in cases involving overdose deaths where multiple drugs were involved, such as when fentanyl is mixed with other substances. The bill does not specify additional funding or implementation timelines. The change would primarily affect drug traffickers and dealers, potentially increasing criminal prosecutions in overdose cases.