You've obviously never been charged with a crime before. If you plead guilty, shit gets dealt with asap, however, you plea not guilty, it takes a long time to get to trial, cases must be prepared by both prosecuter and defence. It's all pretty standard stuff. It's called remand or "dead time" to use the modern vernacular. If they're in solitary, which is doubtful, it's probably at their request or they're a danger or in danger. Protective custody is also an option for the weaker. That's where they keep the rats and diddlers etc.