It's best if you and your spouse can agree on parental responsibilities as you negotiate your divorce, but sometimes that doesn't happen. What happens then?
The first step in Colorado is to file a petition for allocation of parental responsibilities as well as a parenting plan. These plans explain which spouse should be the primary care parent and how you plan to divvy up the decision-making responsibilities.
Again, it's best if you and your spouse can agree on the issues and file a joint parenting plan, but if you can't agree, then you can each file a separate parenting plan and present those plans to a judge.
A judge isn't beholden to either plan, however - the judge can take some from Column A, some from Column B or simply add to the plan on his own.
To determine parental rights, a judge considers the best interests of the child above the interests of the parents, assuming there will be "frequent and continuing contact" between the child and parents. The judge also takes into consideration the child's relationship with you and your spouse, any changes to the child's environment like switching schools or neighborhoods, and the mental and physical well-being of the child and parents.
While there is no legislated age for when a child can determine which parent to stay with, courts generally start letting children make their own determination by age 14, with significant weight to the child by age 16.
Motion to modify
If you or your spouse don't agree with the judge's decision, you can file a motion to modify decision-making responsibility. The court only allows modifications every two years unless the child's safety is in question or if the child's main residence is changing.
A motion to modify decision-making responsibility can only be filed in the same court that created the child support orders. Also, if these modification change child support, you have to file a motion to change your child support agreement.