Legal Question in Criminal Law in Colorado

Re: evidence

Yes, you do, absolutely. You, or your attorney, are entitled to what is called "discovery," which is the evidence the state has. The prosecutors will present witnesses, whose names they must provide, and whom you may investigate before trial and cross-examine at trial.

Re: evidence

The state must disclose the evidence the state has against you. The disclosure comes before trial in the form of discovery.

As for "Can they just go on what someone said?", the answer is "maybe". I suggest you examine the statement, its exculpatory value, its testimonial nature, and the availability of the witness. In short, if you want to fight witness statements, you will need a lawyer.