IF you WITNESS the accident, you should stay at the scene for the purpose of giving a WITNESS STATEMENT to the law enforcement officers.
In this CASE - you must stay to give a statement. END of LEGAL duty.
As to rendering aid - I'll try to be succinct.
As a rule - I DO NOT stop at accident scenes (yes, I have stopped before - but it has to be an exceptional circumstance). This is a personal decision. I DO NOT have red lights, decals, license plate, etc. on my POV that would identify me a nurse or paramedic. I will call 911 and give as much info as I can - exact location, # vehicles, possible resources they may need (fire truck, etc). Stopping at accident scenes that you have no duty to stop (witness) will firmly land you in the 100% accountable for your actions.
Reasons I DO NOT stop:
• Traffic scenes that are "fresh" are very unsafe, No LEO control puts you at the mercy of the scene gods - I've found that they can be punishing.
• No equipment, increases my chance of exposure (blood, haz mat, unstable vehicles, fire, electricity, other drivers, wreckage) - all the while, I am acting in an independent nature - so, if I became ill/injured as a result of my hero actions I alone suffer the consequences.
• Litigation. I know, go save lives - alleviate suffering - yada, yada, but, although I KNOW that I can be prudent and make good decisions and provide excellent care - I just cannot reconcile with the potential for a BAD OUTCOME for me. MVC's are often events that produce injury, injury = pain+suffering+economic damages. This equation makes a lawsuit. I choose not to be a factor.
A CAUTION on the GOOD SAMARITAN laws. Most states have found them to be unconstitutional - a law generally CANNOT limit one's rights to be "made whole"/recover damages. It is also NOT an AFFIRMATIVE defense. As such, I act in a manner consistent with my DUTY to ACT only. ANYONE can sue ANYONE for ANY REASON. Now, they may not win - but, you can bet that defending yourself will not be free/easy.
HoorahFLY - In the case that you describe - NO I would NOT start CPR. Blunt force trauma that has NO VITAL SIGNS on scene has a ZERO 0% factor to survive, no matter what is done. But as a student you probably did not know that. Also, I know of NO STATE that REQUIRES anyone to stop at a scene (unless they are the witness of the accident themselves). This includes NURSES. Now, is there a moral duty (personal choice)?
Anyway, I encourage all to be clear on your state laws.
Know your duty to act.
Make good decisions as it relates to your safety in UNCONTROLLED situations (no training, equipment, etc.). DO NOT become a victim.
The difference between HERO and (scape) GOAT is very narrow.