"In big crime cases there seems to be a lot of prep and discovery done. Why's that?"This was after I had commented about the limited discovery in Virginia.
First, let me say that in many - if not most cases - the only things which could be discoverable are the police report and witness statements. Some jurisdictions give these over (and still win their cases); other jurisdictions refuse. The law and Rules in Virginia allow a prosecutor to deny these to me. It's dumb and things would run a lot smoother if the law required them to be handed over but it's the way things are here.
In big cases there is more to discover. Rule 3A:11 of the Supreme Court of Virginia requires the exchange of reports (ie. ballistic tests, handwriting analyses, etc.). In lesser cases there isn't any of this (except the ubiquitous lab analysis showing the residue was in fact cocaine). The police and prosecutor's office just are not going to pour that kind of money into your client's bad check case. However, in murders, rapes, bank robberies, etc. the money will be spent; these reports will be available.
Furthermore, I think that in more important cases competent prosecutors will give far more evidence then required because of the seriousness of the case. They do this because getting a conviction to stick is more important than playing games. They know that if they convict my client appeals will follow and every moment of the case will be reviewed from top to bottom and it cannot be good for an elected official if a murder conviction is overturned (and, yes, it does happen - even in Virginia). The desire to make sure a serious case is handled correctly can also motivate the judge to make sure that discovery is broader than usual.