Last evening, I watched the Charlie Brown Halloween special with my daughter. As you may recall, every year Charlie Brown is tricked into attempting to place kick a football with Lucy pulling the ball away at the last minute. In this particular episode, she gives him "a signed document" that she will not pull away the ball; Charlie Brown is feeling pretty secure about this. Inevitably, Lucy pulls the ball away yet again, and notes to Charlie Brown that the document was not notarized.
It reminds me of some of my own cases. I often counsel clients to attempt to reach an agreement with their spouse before anyone moves out. Can a signed document protect you in court? It depends...the more comprehensive and agreement is, and if both parties have attorneys, the more protection the agreement can provide. Sometimes, particular clauses of an agreement are simply not enforceable, for example, an agreement to waive child support will likely not be enforced by a court. Notaries are necessary for some documents, like deeds, and for settlement agreements can be helpful. In any case, getting the advice of an attorney is always the best option to decide if an agreement is enforceable and legal. Being trusting can be an admirable quality, but don't end up on your back like Charlie Brown.