Contact the innocence project.
The above information does not establish an attorney client relationship nor is it meant to provide legal advice.
An appeal after her conviction would've been the first and best means to challenge the conviction. Failing the normal appellate channels, a writ of habeas corpus would be another approach. You can contact an appellate attorney for a free consultation about what can be done and an estimate of how much it would cost. You can also contact the Innocence Project at CalWestern School of Law and see if they're interested in reviewing the case.
Law Office of Andrew Limberg, APLC 380 S. Melrose Dr., #329 Vista, CA 92081 (760) 806-4381
Contact locally experienced appellate counsel. Three of the best I know of in San Diego are Charles Sevilla, Pat Ford, and Al Macina.
Law Offices of David Shapiro 3555 4th Avenue San Diego, CA 92103 (619) 295-3555
First of all, how do you know what your sister's lawyer said to the judge at a sidebar? You should hire an attorney to look into it. Your questions raises too many other questions in my mind. You don't know for sure that the new trial motion was denied for that reason alone. The lawyer's decision to not call the alibi witnesses could have been a tactical decision based on the strength of the evidence thus far in the trial.
Do you know whether there was an appeal? Do you know whether your sister's lawyer investigated the alibi witnesses?
Any advice given is limited to the scope of the information that was provided in the question. Please do not take anything in the answer as a guarantee of a specific result in court. There is no way to be sure of an outcome until it happens.
You need to consult with an appellate lawyer in your area. Further, you need to make sure you have the facts exactly correct, and an attorney could help you with this. As my colleague notes above, I find it hard to believe you know what was said at a side bar. I have found that there is often a difference in what people (perhaps your sister) hear and what was actually said.
SLG Criminal Law Group
515 South Flower Street
Los Angeles, CA 90071