Does a promise to appear in 2009 effect a Serna motion when defendant finally arrested in 2012 on the underlying misdemeanor?

The time issue on the Serna motion is tolled when the defendant was in flight from the underlying arrest and prosecution. The idea behind this motion is that the basic due process right to a fair and speedy trial is presumed to be "harmed" by the DA's failure to prosecute a case within a year or so from the initial arrest. You argue that it is difficult to put on an effective defense after a year of waiting to be prosecuted. However, in this case it appears that the new arrest is an arrest on a fresh violation from the failure to appear on the 2009 offense. If an attorney were to file this motion, it would surely be denied given that there is not the underlying "evil" present which the motion is intended to prevent. In short, a Serna motion is not the best avenue of defense in this case. Good luck.

I think that you may have enough here for a Serna, but it depends on the facts of the case specifically. There may be other defenses that are available. It is advisable to meet with an attorney to discuss the case in more detail.