Earn a Master's degree or Bachelor's degree in a related field. Normally, to enter a Ph.D. program in criminology, you must have master's in the field or a related field, such as criminal justice, law or forensics. Your grades during the master's program should also be average or above average.
Complete the required coursework. In order to earn your Ph.D., you will need to take a number of related courses. How many courses you take usually depends on your prior educational experience in the field. You may take anywhere from 20 to 40 credit hours.
Write a dissertation based on original research. Many Ph.D. programs require you to conduct research in the field of criminology and write a dissertation of more than 50,000 words.
Complete a dissertation defense. During the defense, you must convince a university committee of your dissertation's applicability to the realm of criminology.