A divorce that involves children culminates in a final order that resolves issues having to do with (a) property and (b) children. The part of the order that deals with property is final (and can't be changed) after 30 days. The part of the order that deals with children - child support, custody, and visitation - is subject to modification by the court if there is a significant change in circumstances.
The idea behind this is simple: When the children are five years old, Dad may be an alcoholic and a drug addict, and Mom may be a sensible person, a solid citizen. The parties get a divorce; the Court makes a ruling based on the circumstances that exist at that time. Six years later, things have changed. Dad has gotten his life together. Mom now faces an indictment for child abuse. The old order is no longer appropriate and is no longer in the best interest of the children.
The Texas Family Code (section 153.002) says that in any custody case, the "primary consideratoin" is the best interest of the child.
The Texas Constitution (Article I, Section 3a) and section 153.003 of the Family Code state that gender discrimination isn't allowed. This means that the father is NOT at a disadvantage if he seeks custody of his 3-year-old son; there's no such thing as a "tender years doctrine." The law sees him as being on exactly the same legal footing as the mother.
If a child is age 12 or older, he can file a written statement (called a "Preference") which tells the Court which parent he wants to live with. It isn't binding on the Judge (or jury), but it is one of the factors to be considered in the case. In cases involving a 16- or 17-year-old, the Judge will tend to go along with the "child's" wishes unless there's a good reason not to.
Technically, there is no age at which a child can "choose which parent he wants to live with." I once tried a case to a jury where the child (age 13) had filed a statement with the Court saying that he wanted to live with his mother; he also testified, at the time of trial, that he wanted to continue to live with her. I represented the father. I was able to convince the jury that despite the child's wishes, he'd be better off with his father; we won the case.
Child custody can be a jury issue, if somebody pays the jur fee ($30.00). "Visitation" (the actual terms and conditions of access to the children) is still decided by the Judge — not the jury. One party may "win" the jury verdict, but the Judge can then award possession on a 50-50 basis.
The factors that figure into a custody fight also figure into a case where the only issue is the modification of visitation. The Family Code (section 153.252) says that there is a presumption that a
"standard possession order" for the "visitation parent" is in the best interest of the child.
The legal fees for a full custody fight can exceed $25,000.00, and I'll get a large retainer up front.
Often the difference between the "parenting abilities" of the two parents is very subtle and is difficult to prove. In a "close case" (which many of them are), you may have to hire a psychologist to evaluate the parties, and testify for you at trial. This will cost several thousand dollars.
To prove what is in the best interest of the child, you want to show (1) what is GOOD about you as a parent and (2) what is BAD about the other parent. Some of the factors are:
1. which parent has participated in the children's activities;
2. which parent attends most of the parent-teacher conferences;
3. any aspects of a parent's past which reflect negatively on him, such as suicide attempts, mental illness, criminal convictions, alcoholism, chronic health problems, family violence, or drug addiction (these would be things that happened SINCE the last order);
4. the ages of the children (very young children may be "closer" to their mother).
Custody contests almost always involve a "social study." In Dallas County, the fee for the social study is calculated thus: each party pays the equivalent of 1.5% of his net annual income. The social study is done by Dallas County social services. If a private individual were to do the social study (as is customary in Collin County), it could cost thousands of dollars, with each parent (usually) being ordered to pay half the cost. A "social worker" will visit you in your home (and the other party in his home) and gather information about your situation, employment, and background. This social worker then writes up a report and sends it to the Judge. The social worker can also testify at your trial, and his opinion carries a great deal of weight.