Am I sinful for having concealed a secret about a fatal hit-and-run accident, the perpetrators of which have not yet been discovered, after a friend confided in me about it 8 years ago?

The questioner cannot bear witness to the accidental killing because he did not see it himself. Testimony requires personal observation, and testifying based on information from others is incorrect. His friend, who witnessed the accident, cannot have his testimony accepted after ten years without an excuse, because delaying the testimony for this period discredits the witness. The only solution is for the questioner to try to persuade his friend, who was driving the car, to make an admission before the Sharia court so that the deceased's 'Aqila (kin responsible for blood money) who are entitled to the blood money can be identified.