The law contains a very slight – but possibly very significant – distinction between a modification seeking a change in visitation and a modification seeking a change in custody.

For a modification of visitation, the party seeking the change must prove only that modification of visitation would be in the best interests of the children. There is no requirement that there has been a substantial change in the circumstances of the child or of the custodial parent.

For a modification of custody, the party seeking the change must claim and prove that a substantial change has occurred in the circumstances of either the child or the custodial parent.

A motion to modify sole physical custody to joint physical custody may be a difficult undertaking. The law presents a strong preference for joint physical custody with a scheme for sharing parenting time that allows each parent to have “significant” but not necessarily equal time with the children. If the previous court did not award joint physical custody, the burden of showing a substantial change of circumstances will be high.

Most often, success in such situations is due to children becoming older. Babies and toddlers have significantly different needs than elementary-aged school children and as children enter high school, their wishes regarding custody are generally given more weight by St. Louis County judges.

Because of the difference in the burden of proof in the different situations, the appellate courts have directed that care must be taken in how physical custody is designated. Specifically, in November of 2020, the Eastern District of the Missouri Court of Appeals (where St. Louis City and County are located) has ruled that what is often referred to as a “Siegenthaler” schedule (essentially an arrangement where the children live with one parent and see the other parent one night a week, every other week-end and half of the holidays and the summer) is not joint physical custody. Therefore, in a situation where one parent has Siegenthaler-type time with the children he or she must show a substantial change in their circumstances or those of the children to establish the right to joint physical custody.

Of course, joint physical custody does not automatically mean equal or 50-50 custody, but that is the default meaning to the overwhelming majority of St. Louis judges. In reality, if a judge wants to modify a judgment to award joint physical custody, they can fashion a judgment to that effect that will stand up on appeal.

As attorneys, we often denominate a schedule where the time given to one parent is Siegenthaler-type visiation “joint physical custody” just to settle the case (it is amazing how inportant it is to some parents to be able to say that they have “joint custody.” At the risk of being cynical, the judge is going to do what they want on any subsequent modification and they can justify ther result regardless of the label originally applied.


In St. Louis County, it is rare for judges to modify an order of sole legal custody to one parent to award joint legal custody to both parents. There is a strong preference for joint legal custody in St. Louis County, without respect to the arrangements for parenting time with the children. If joint legal custody was not awarded, it is because the judge believes that the parents are unable to make shared decisions about the welfare of their children. Joint legal custody may be ordered by the court even where there is some level of tension and hostility between the parents on a personal level so long as the parents have the willingness and ability to fundamentally cooperate in making decisions regarding the children’s upbringing. Joint legal custody will always be considered and may be awarded even if one party objects. As such, if the judge found such lack of harmony, it is difficult to prove that the situation has totally improved if one parent continues to object to joint legal custody.