Suppose a person was driving a car in Australia with an unrestrained child. An unavoidable crash occurs where there are no other vehicles involved, and the child dies as a result.
With what crimes would the driver likely be charged?
According to a page at StacksLaw.com (website of Stacks Law Firm), Australian law on death by unnatural causes is state-based but with little variation. As Australia is also a common law jurisdiction, this tradition has legal relevance as well.
For New South Wales, the appropriate offence would be involuntary manslaughter under common law which consists of
killing by an unlawful and dangerous act, that is, any intentional act by a defendant which is unlawful and dangerous and carries an appreciable risk of serious injury, and which causes the death of another person
or, the more important definition,
killing by criminal negligence, that is, any act or omission by a defendant, which causes or accelerates the death of another person, in circumstances where the defendant was under a duty to care for the deceased person, and the acts/omissions amount to gross negligence (or perhaps recklessness) and a failure to perform the duty.
This duty arises, in NSW, from Part 16, Rule 266 of the Road Rules, in particular paragraph (1) which says
The driver of a motor vehicle (except a bus or motor bike) that is moving, or is stationary but not parked, must ensure that this rule is complied with for each passenger in or on the vehicle who is under 16 years old.
where the rule makes requirements for various types of safety restraint based on age bands.
This is supported by a similar page at ArmstrongLegal.com (the website of Armstrong Legal), which also describes the penalty:
The maximum penalty for manslaughter is imprisonment for 25 years.