If you do everything within your scope of practice and someone dies anyway...you did everything you can do. If you as a non-professional stick a needle in someone’s chest and they die, you could end up with massive civil liability or even go to prison, depending on the law where you live and the circumstances. But I’m not a lawyer.

A chest seal is likely to keep someone alive to get them to definitive care, if applied correctly in time and the patient has tension pneumothorax. More, vented chest seals is better. I have been formally trained on decompression needle usage, and I would start with a chest seal every time.