Explain the flaws of Utilitarianism?

Utilitarianism is a legal doctrine formulated by Jeremy Bentham in the 18th century, it is a consequentialist school of thought which locates the morality in the consequences of an act. Exemplified by the Lifeboat case of 1884, where the stranded crew of over 18 days, over 1000 miles away from shore, believed that is was morally justified to kill one crew member in order to save the lives of the other three members of the ship. The flaws of utilitarianism is shown in the example however, as the crew members were later charged with murder. Bentham failed to acknowledge that the quality of acts is also a factor, and that despite the crew members acts creating 'the greatest good to the greatest number', meaning that more people saw benefits to their actions, the doctrine fails to acknowledge the rights and duties which are owed to the crew member who was killed, this is known as categorial morality, where morality is located in certain duties and rights regardkess of the consequences.