Depending on your research question and how much is already known about the topic, you can choose to conduct unstructured (in-depth) interviews, semi-structured interviews, or structured (standardised) interviews. In unstructured interviews, only the topic and the initial research question are fixed. Semi-structured interviews use previously formulated questions, but allow you to adapt their order and exact phrasings to the flow of the conversation. Structured interviews use a fixed order of closed questions with fixed answer categories. Hence, unstructured or semi-structured interviews are probably more suitable than standardised interviews when you want to explore how a newly introduced law operates in practice, for example. Vice versa, when you want to find out more about the practical effects of a law that has been around for a long time, semi-structured or even standardised interviews may be a better choice.

One important guideline to take into account when preparing your interviews is to be sure about what exactly you want to know. Are you interested in facts, reasons behind the facts, opinions, and/or experiences? After all, your research goals determine what topics or questions you should put on your interview instrument (which is often called a topic list). For example, you may be interested in how fairly people feel treated during legal procedures (experiences) or the reasons why a certain law was adopted (reasons behind the facts). Other important aspects of preparation include reading relevant literature, familiarising yourself with what your respondent has already written about the topic (if applicable), considering which information you should provide to respondents beforehand, deciding on the location of the interview, and gathering relevant equipment (such as a recording device).

At the start of the interview, it can be helpful to summarise or repeat the aim of the interview and indicate its contents, structure and duration. This is also a good moment to discuss issues of anonymity and confidentiality, and to ask for permission to record the interview audio if you would like to have a literal transcription of the conversation to use for data analysis. An alternative is to just take notes during the interview and elaborate them afterwards, preferably directly after the interview when your memory is still fresh. These issues are all part of the process of getting informed consent: you need to inform respondents about the contents of the research, making clear that participation is voluntary and consensual.

During the interview, careful listening is key. Thus, rather than treating your topic list as a to do list and worrying about the next question while your respondent is still answering the previous one, you should really pay attention to what the respondent is saying and ask follow-up questions if needed. These probes can take the shape of full-fledged questions or of “non-specified encouragement (‘uh’, ‘yes’, ‘yeah’)” (Boeije, 2010, p. 63). It is also important to be aware of the power dynamics that play a role during interviews. The balance of power between the interviewer and the interviewee will be very different, for example, in interviews with legal professionals (such as Supreme Court judges and special prosecutors) versus vulnerable participants (such as victims and children).

At the end of the interview, when you have covered the topics on your interview instrument or at least the most important ones, it is often advisable to ask if there are any topics that have not yet been discussed but which the respondent deems important. You should also offer to send the transcription to the respondent to correct any factual mistakes, and potentially a summary of your findings after the research has ended. And, of course, do not forget to thank respondents for their time!