For negligence that results in the death of a human being, many legal systems make a distinction between negligent homicide and criminally negligent homicide. Where the line is drawn depends on a judgment call, but in general you're found criminally negligent if your actions are completely unreasonable.

A good example might be this. In one case, a driver's brakes fail and he hits and kills a pedestrian crossing the street. It is found that he had not done proper maintenance on his brakes, and the failure was preventable. He's found liable in a civil case, because his negligence led to someone's death, but he's not found guilty of a crime, so he won't go to prison. A different driver was speeding, driving at highway speeds through a residential neighborhood. He turns a corner and can't stop in time to avoid hitting a pedestrian. He is found criminally negligent and goes to prison, because his actions were reckless and beyond what any reasonable person would do.

The first case was ordinary negligence: still bad because it killed someone, but not so obviously stupid that the person should be in prison for it. The second case is criminal negligence, or in some legal systems it might be called "reckless disregard for human life". He didn't intend to kill anyone, but his actions were so blatantly stupid that he should go to prison for causing the pedestrian's death.