In Minnesota, there are two parts of the custody issue. First, there is "Legal Custody" which is the right of a parent to co-parent the child by mutually deciding important issues of the child's life, such as education, religion, medical treatment, elective surgery, discipline, and residence, unless the order already directs the decision in that issue. There is also "Physical Custody." This is the physical residence of the child and the decision making on a day to day basis, such as clothes to be worn, food for various meals and so on.
In both of these types of custody, there is both sole custody to one parent, or joint custody, which is custody shared between the parents in some way but not necessarily equally.
These are labels and the courts are stressing more and more that they are nothing more than labels. The current focus is upon the Parenting Time. Parenting time is set by a schedule usually in a Parenting Plan or in the Custody section of a Paternity Decree or Marriage Dissolution Decree. The amount of parenting time is generally measured by counting the number of overnights in a year or in a month for purposes of calculating child support. The Parenting Expense Adjustment is increased based upon more time in both households so that if most time is in one, such as a case where the parenting time is less than 10% in the Obligor's home, there is no Parenting Expense Adjustment.
The statute creates a presumption, that if there is nothing seriously wrong with a parent, at least 25% goes to the non-custodial parent, (a parent whose co-parent has sole custody.) Joint legal custody is also very commonly awarded and sole legal custody is generally reserved for those parents who cannot cooperate successfully on even the most important things of life. Domestic violence is sometimes taken as an indication of such a gross inability to respect the opinion and the input of one of the parents.
Custody is decided based upon the analysis of the court of 12 factors as they apply to the facts of the specific case. No one factor is allowed to decide the entire matter and if it is contested, the court will make findings on each factor and the implications it has upon the custody decision.
Likewise, custody agreements should anticipate that requirement and state in some manner how the factors guided the agreement. In stipulations, however, this is sometimes abbreviated by saying it is in the child's best interests that parents share joint legal custody.
Parental Alienation is where one parent causes the joint children to dislike the other parent. Proof of this is difficult in Court, but if a court, a Guardian Ad Litem or a Custody Evaluator finds one parent is making the other a villain or disparaging the parent to the children, it is likely to be held against the person doing that. It especially pernicious when custody cases are pending because it is done then in order to gain an unfair advantage against the other parent.
It is also likely to come back to haunt the alienating parent later when the child sees what happened as an adult or teen looking back. It also causes the case to be more involved, more likely to require a credentialed mental health provider to act as an expert and therefore more expensive.