Yes, there have been instances where someone has been found guilty and sentenced after they were dead. This usually happens in cases where the individual was on trial before their death, and the legal process continued after their passing. The legal principle is often referred to as "abatement ab initio" or "abatement by death."
When a defendant dies before their trial or appeal process is completed, the charges against them may be dropped due to their death. However, in some cases, the legal system may choose to proceed with the case for various reasons, such as the significance of the case, the need for closure for the victims or their families, or to set a legal precedent.
If the legal process continues despite the defendant's death, the court may enter a judgment of conviction against the deceased person. However, the actual sentence may not be imposed since the person is no longer alive to serve the sentence. In such cases, the judgment may be considered a historical record of the court's decision, but it does not have any practical impact on the deceased person.
It's worth noting that the specific laws and procedures related to posthumous criminal cases may vary depending on the jurisdiction and legal system involved.