Case studies are often used to illustrate the type of decisions practicing engineers may have to make. There is no one single source for engineering ethics case studies.
The NSPE has created a searchable database of their Board of Ethical Review cases
The Markkula Center for Applied Ethics has collected engineering ethics case studies that can be browsed by category
The Ethics Education Library has a Case Studies Collection that includes engineering ethics case studies.
The Online Ethics Center for Engineering and Science includes a collection of cases for teaching engineering ethics
Engineering Case Studies collection from Alexander Street is another possible source. The collection includes video and text material about engineering failures
Individual engineering ethics case studies can be found by searching the Compendex database.