The short version of the Japanese justice system is "Guilty until proved innocent", instead of (as in most modern countries) "Innocent until proved guilty". In addition to that, focus is much more on confessions instead of investigation - the latter exists of course, and is used for finding the culprit (as happened when we had a burglary at our house. They got the guy one year later). When someone is in custody though.. then it's about getting a confession.

This can definitely be problematic, particularly when considering the conditions during custody. No lawyer.. or much of anything, except massive psychological pressure.