There is probably a docket control order or scheduling order in place. If so, you should read it carefully and determine what the judge ordered the parties to do in terms of designating testifying expert witnesses. I do not practice family law, but in the civil district courts of Harris County, the standard DCO explicitly says that formal, written designations of testifying experts are required to be served by all parties by specified dates. Unless the family courts have different orders or rules, I'm afraid that since your designation deadline has passed and you have not designated, you are now at risk of the judge not permitting you to call the expert witness you refer to as a trial witness. I doubt that the fact that the court appointed the expert will make any difference or excuse you from an order requiring a written designation to be served by a certain date. Also, court appointed experts, like almost all other expert witnesses, generally do not show up and testify at trials automatically. Whoever wants to call an expert to testify needs to hire the expert and agree to pay for his or her services. This needs to be done a substantial period of time prior to trial so the expert can do the necessary work and prepare to testify.
It sounds like you don't have a lawyer. If that is the case, with all due respect, you are making a great mistake. Failing to designate your testifying expert on time is probably only one of the missteps you have made so far. If your spouse has a lawyer and you don't, your chances of a good outcome are even worse because your adversary knows what to do and how to do it correctly. Of course, you could try to settle your case, but because you have no lawyer, your bargaining position is relatively weak, making it very difficult for you to drive a good bargain. Unless there is a settlement, there will be a trial. If you are like most lay people, you know essentially nothing about any of the many procedural and substantive rules of law that govern trials and you will probably lose representing yourself because of that, regardless of the merits of the case.
I strongly advise you to hire a lawyer right away. Houston has many fine family law lawyers who charge reasonable fees. Get one who is certified in Family Law by the Texas Board of Legal Specialization. A link to the board's website appears below.
The answer is - it idepends on the judge. To be safe, designate him anyway, both as an expert and fact witness. If opposing counsel argues, then make your argument that the expert was already designated by means of the Temporary Orders.
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