It sounds like a lot may be at stake in your situation. Over the last 30 years, the burden of proof in protective order cases has shifted pretty dramatically in favor of the (alleged) victim, meaning, most judges would rather err on the side of safety than take a chance.
Does your order prohibit all contact, or are you and your girlfriend permitted to communicate in some way? If you are prohibited from any contact, your current communication may be a violation of the Order. Do you think it is?
Was a domestic violence victim advocate, as they are called, assisting your girlfriend in filling out the protective order paperwork?
If your girlfriend asks the Court to remove the Order there are several things both of you can expect. The Judge may quiz your girlfriend fairly vigorously as to her state of mind, e.g., fearful, and why she filed in the first place if she is asking to remove the order 2 or 3 weeks later. She may also be counseled by any victim advocate who was involved. While I've seen it done, it is not all that common for protective order withdrawal requests to be granted.
There is a serious threat that if the protective order is withdrawn that your girlfriend's ex-husband and his attorney can try to take custody of their son, and/or restrict access to her and you.
Is anyone involved in counseling?
One idea may be for both you and your girlfriend to seek therapy, as that is often looked upon favorably by judges. It should be with therapists who are familiar with the dynamics of domestic violence and the variations, such as yours, that occur. The point would be to 1) address any threatening behavior on either your or your girlfriend's part, 2) to help stabilize your relationship and, if possible given the current custody order, 3) to get some therapeutic support for the boy.
Affordable therapy is often available at community mental health centers or your local Mental Health Association. Although many people are reluctant to go into therapy, what the Courts like is to see a significant period of therapy (6 months, maybe), with a very brief report to the Court that real progress has been made. Plus, it rarely hurts to get supportive therapy for a child involved with a crazy dad and a mom who has had some conflict with her boyfriend/fiancee.
There is a catch, though, and that is that the ex-husband's attorney can try to go after the therapy records. So the very first subject for discussion with the counselor should be confidentiality and the limits thereon, given active court cases.
If you need more help or have follow up questions, please let me know.
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