When scientists act unethically, their actions can cause harm to participants, undermine knowledge creation, and discredit the scientific community. Responsible Conduct of Research (RCR) training is one of the main ways institutions try to prevent scientists from acting unethically. However, this only addresses the problem if scientists value the training, and if the problem stems from ignorance. This study looks at what scientists think causes unethical behavior in science, with the hopes of improving RCR training by shaping it based on the views of the targeted audience (n = 14 scientists). Previous studies have surveyed scientists about what they believe causes unethical behavior using pre-defined response items. This study uses a qualitative research methodology to elicit scientists' beliefs without predefining the range of responses. The data for this phenomenographic study were collected from interviews which presented ethical case studies and asked subjects how they would respond to those situations. Categories and subcategories were created to organize their reasonings. This work will inform the development of future methods for preventing unethical behavior in research.