The ethics of photography are complex and ever-changing. In general, however, it is considered unethical to take photographs of people without their consent. This is especially true when the photographs are likely to cause harm or distress. In the case of the Nikki Catsouras death photos, the tow truck driver who took the photos was clearly violating ethical standards. He took the photos without her consent, and he knew that they would cause her family and friends great pain.
Nikki Catsouras Death: Disturbing Photos of a Tragic Accident