This is the way to do it, with wintesses, and not in the same lawsuit per your other question.
The above is general legal and business analysis. It is not "legal advice" but analysis, and different lawyers may analyse this matter differently, especially if there are additional facts not reflected in the question. I am not your attorney until retained by a written retainer agreement signed by both of us. I am only licensed in California. See also avvo.com terms and conditions item 9, incorporated as if it was reprinted here.
Law students spend weeks on this question. Generally, you cannot prove your case by showing that the defendant is the type of person who would do such a thing. But you can show identity, a common scheme, a plan, or a motive. How strong the similarity must be depends on what you are trying to prove.
Before you bring these other people into court, make sure that your evidence linking their damage to the perpetrator is strong. The court does not want to have a long trial regarding his involvement with these other people if they are not asking for damages.
Yes, you can bring and call any witnesses who may be helpful to you in proving your small claims court case. However, the judge can decide that these witnesses' testimony is not relevant to prove that the defendant caused you damage in your case.
Frank W. Chen has been licensed to practice law in California since 1988. The information presented here is general in nature and is not intended, nor should be construed, as legal advice for a particular case. This Avvo.com posting does not create any attorney-client relationship with the author. For specific advice about your particular situation, please consult with your own attorney.