The Paramount Principle
Section 1 of the Children Act 1989 provides that when a court determines any question about a child's upbringing, the child's welfare is the paramount consideration. Not the most important consideration -- the paramount one. Everything else is subordinate to it.
This means the court is not trying to find a fair outcome for the parents. It is asking one question: what arrangement is in the best interests of this child? Every argument you make must be directed at this question.
The Welfare Checklist
Section 1(3) of the Children Act sets out the factors the court must have regard to: the ascertainable wishes and feelings of the child, the child's physical, emotional, and educational needs, the likely effect on the child of any change in circumstances, the child's age, sex, background, and any relevant characteristics, any harm the child has suffered or is at risk of suffering, the capability of each parent to meet the child's needs, and the range of powers available to the court.
These factors are not a tick-box exercise. The court weighs them all together. In a given case, some factors will carry more weight than others.
The Child's Wishes and Feelings
Courts take the child's views seriously, but the weight given to them depends on age and maturity. A 15-year-old's expressed wish to live with one parent will carry significant weight. A 4-year-old's preference will be considered but interpreted with great care, particularly where there are concerns about parental influence.
CAFCASS officers are trained to ascertain children's wishes and feelings in a way that minimises the risk of influence. If a child's expressed wishes appear to reflect coaching by a parent, the court and CAFCASS will investigate this carefully.
The Harm Consideration
The court must consider any harm the child has suffered or is at risk of suffering. Where domestic abuse is alleged, the court must consider the impact on the child of witnessing abuse, not only the risk of direct physical harm.
The harm consideration works both ways. Harm from contact with an abusive parent is relevant. But so is the harm to a child of being prevented from having a meaningful relationship with a loving parent without good reason.
Capability of the Parents
The court assesses each parent's capability to meet the child's needs. This includes practical matters -- stable housing, employment, childcare -- but also emotional capability: the ability to prioritise the child's needs over the conflict with the other parent and to support the child's relationship with both parents.
A parent who demonstrates throughout proceedings that they are focused on the child's wellbeing -- not on winning the dispute -- will make a better impression than one who is focused on defeating the other parent.