Legal Question in Criminal Law in California

There is no way to answer your question without more information.

Once possibility is that the District Attorney reviewed the police reports and decided there was enough evidence to file charges on some suspects, but not all of them.

District Attorneys generally can drop charges against any defendant at any time even after a trial has started. However, since you have not included any facts in your question it is impossible to be specific as to your situation. Therefore in general the answer to your question is yes, a co-defendant's charges can be dropped independent of the other defendant or defendant's depending on the situation. However each situation is unique.

Any answers provided in this forum do not constitute legal advice and should not be relied upon as legal advice. The communications between the attorney and the person or persons asking the question or questions do not create an attorney-client relationship. There is also absolutely no client confidentiality created by answering questions in this manner. Any answers provided by this attorney are not to be considered legal advice and do not create any type of attorney-client relationship.