Hi there,
A custody battle is generally a nightmare, but with BPD/NPD, it's an order of magnitude worse.
I think I'd advise that since you're dealing with a custody case here, the well-being of the children comes first. Let's do a thought experiment. Let's say you order a psych eval, and it comes back that your ex has BPD. I'd ask, so what? Parents can have all sorts of issues--physical, mental, financial, etc.--but nevertheless they're still able to parent. So I think that what it comes down to is whether your ex is abusive, negligent or otherwise not capable of caring for your kid(s) properly. My point is, it's not so much the diagnosis of BPD that's important; it's the behaviors that adversely impact the kid(s) that matter. Things like screaming at the kid(s), insulting them, humiliating them, hitting them, scaring them, threatening them, punishing them excessively, blaming them, and making them over-function for their mom, becoming HER emotional caretaker and HER servants instead of the other way around, the way it's supposed to be. You need to document a pattern of abuse in my opinion.
I have an ex BIL who is undiagnosed NPD and has a highly dysfunctional life, and who was also extremely combative in court, being an ex lawyer himself. It took the courts a long time to "see through" his ploys--but once they did, they came down hard on him. Basically they found him in contempt of court, and his parenting time was severely restricted, requiring supervision by another adult all times.
How did the court get there? Well, CPS was involved, twice, and a GAL was appointed. The GAL's investigations took several months. And though a Cluster B can seem to "pull themselves together" for a short time, I think they don't have the stamina or consistency to "fake" it for very long. Their self-destructive tendencies eventually shine through. For my BIL, that included heavy drinking (and failing multiple breathalyzer tests), several missed appointments and court dates, the inability to produce requested documents, non-compliance with child support and general non-cooperation with court orders. On top of that, in the intervening months he had run-ins with police and a few medical events, one requiring a long hospitalization. In addition, he had a long track record of skipping visitation and neglecting to call his children when he had agreed to do it. Together with the GAL report and recommendations, the courts saw through his BS and came up with a reasonable custody arrangement. It was one of the very, very rare cases that wasn't settled and actually went to trial, because my ex BIL was so stubborn and refused to cooperate or negotiate.
But central to all that was demonstrating, not that my ex BIL was mentally ill, but that his parenting was inadequate for the children. In his case, things like spotty driving/accidents, reports of not feeding the children, not attending to normal parenting duties (e.g. PTA meetings, doctors appointments, dental visits, kids' activities, etc.), parentification, allowing the kids to see porn/inappropriate movies, abusive language/insults and an unclean home were important in building the "case" of not being fit to parent on his own. His inability to care for his own health issues (untreated diabetes, kidney failure, gout, alcoholism) also played a part.
Hope that perspective helps a little.


