To do really well in a medical law exam you need to show a good understanding of the law (of course!) but also a good knowledge of the ethical principles. This can worry students: should I be spending more time writing about ethics or more time writing about law? Your lecturer may have given you specific guidance on this. For most courses it is important to make sure you include both. An essay which is full of cases but fails to mention a single ethical argument is unlikely to do well. But neither would an essay which cited many great ethicists, but neglected to refer to a single case.