Although it's not particularly common in the DUI and run-of the mill general cases I accept normally as a Denver criminal defense lawyer, co-defendants are fairly common in larger and more complex Colorado criminal cases. And they bring up a number of interesting issues. A big one, which I'll cover here, is a serious issue of attorney ethics. If you and a friend are charged with say conspiracy to distribute drugs, the prosecutor may charge the two of you together. He may bring the same evidence and the same charges against both of you. It may sound like a good idea to share a lawyer (or a couple lawyers, if it took a whole crew to distribute the drugs, it might take more than one Denver criminal defense lawyer to help you out). That will save you money, and keep you on the same side for the moment.
The problem is when there is a situation where the attorney must sort of choose sides. What if it comes out that one defendant is believed to be more culpable by the prosecution? The prosecution would then probably seek the testimony of the other defendant, in exchange for possibly a sweetheart deal. At that point, how does the attorney provide competent representation to both parties? He knows that if he advises the second defendant to take the plea, he will be screwing over the first defendant. But on the other hand he also has an obligation to make sure the second defendant gets the best outcome in this case. The attorney may even question if he can continue representing either party, since he will have information from both given to him in confidence. The conclusion is, your friends may not stay your friends if you are charged with a crime. Also, please hire your own lawyer, don't split one with a friend.