The following are some suggestions in terms of how to deal with situations where mutual abuse is alleged. First, a neutral party should verify the incident with a police or medical reports. This neutral third party is most often the court appointed guardian ad litem. Police reports and medical records can often provide a critical guide as to what has happened. If someone was injured, this will often reveal itself in medical records. If medical records show that one party was injured, this is often dispositive in terms of what type of abuse took place.
In terms of police reports, parties will often make important admissions and statements at the scenes of incidents that can have a bearing on what happened. If one party admits that they abused the other, for example, it will often be dispositive for the courts.
In many cases, the police might not have been called. In other cases, they may have been called, but there might not have been any admission at the scene or medical injury. In these instances, it is important for the incident to be corroborated by a neutral third party, like a neighbor. Neighbors and third parties can often lead credence to allegations of abuse so long as they are neutral and not overly aligned with one party or the other.
Apart from the above, it can be important to look into the past of the parties when abuse is alleged. If one of the parties has a prior history of arrests, violence and related actions, it does not necessarily mean that they are the culpable party here. However, it is a factor that cannot be overlooked in these situations because far too often a party who commits domestic abuse has a pattern of doing so. On the flip side, the opposite can also be true when a party has no criminal history or pattern of violence throughout their life.
Further, if one of the parties suffers from a mental illness or personality disorder, this is not always dispositive, but it is a factor that cannot be ignored. Those who commit acts of abuse, and/or trump up allegations of abuse, can often suffer from mental illnesses and/or personality disorders. In cases where there are no physical injuries, any witnesses to corroborate the abuse, and the alleged abuser has no history of violence in their life, the allegations may prove to be false.
In some cases, custody evaluations and psychological evaluations can be critical components in determining what has and has not happened. A custody evaluator for example can often get the perspective of all the parties, including the children, and can often lend guidance to the court about what might be happening, in terms of abuse. In assessing credibility, the professional will often investigate when the allegation were made, the timing of disclosure, and stage of legal proceedings.
 Peter Jaffe, Janet Johnston, Claire Crooks and Nicholas Bala, Custody Disputes Involving Allegations of Domestic Violence: Toward a Differentiated Approach to Parenting Plans, 46 Fam. Ct. Rev. 500 (2008).