Alternate jurors are not allowed in the jury room during deliberations. Although the defendant did not object at trial, the right to a 12-member jury is a waivable-only right that does not require timely objection. Furthermore, the right to a 12-member jury is protected by the Texas Constitution in Art. V, §13 [1]. This right precludes the deliberation of more than 12 jurors. Using a harm analysis, it could not be found, beyond a reasonable doubt, that the alternate juror did not contribute to the defendant’s conviction or punishment because she was instructed by the court to participate in deliberations. Trinidad v. State, 04-07-00799-CR [2].
Links:
[1] http://tlo2.tlc.state.tx.us/txconst/sections/cn000500-001300.html
[2] http://www.4thcoa.courts.state.tx.us/opinions/htmlopinion.asp?OpinionId=21314