Announce you are recording him before you start recording him. Then start recording him. California is an all party consent state, so you can record if you have permission of all involved. If he stays on the line, that would be implied consent. Same with in person.
If the harassment reaches a high enough level, call the police about it and file a report.
I am licensed in Pennsylvania. Members of my firm are licensed in various states, including Pennsylvania, New Jersey and New York. We handle cases involving personal injury (car accidents slip and falls, etc.,) medical malpractice, nursing home abuse, workers' compensation and social security disability. This post is not legal advice, but instead contains general educational information. Please do not act or refrain from acting based upon what you read in this post. Also please remember that this post does not form an attorney/client relationship between you and me. If you have specific legal questions, you should contact an attorney in your state for assistance.
I agree with attorney Ellis.
Announcing that you are recording the conversation gives the other person the opportunity to either shut up or continue. If they shut up, then your mission is accomplished. If they continue, then you have made a record of their abuse.
You have the right to be free from abuse, even verbal. A DV Restraining Order may be in your near future.
More importantly, your child has the right to be free from his anger. If he is insulting their mom in their presence, then this is a form of child abuse.
Legal disclaimer: The response given is not intended to create, nor does it create an ongoing duty to respond to questions. The response does not form an attorney-client relationship, nor is it intended to be anything other than the educated opinion of the author. It should not be relied upon as legal advice. The response given is based upon the limited facts provided by the person asking the question. To the extent additional or different facts exist, the response might possibly change. Attorney is licensed to practice law only in the State of California. Responses are based solely on California law unless stated otherwise.
I agree with my colleagues, but I'm also concerned about the child. You don't want to have these issues during a visitation exchange -- not only are they awful enough, but anything out of line in the presence of the child must be avoided. You would be well-advised to discuss this situation with a family lawyer. He or she will be able to advise you regarding all issues you raise here. Best of luck to you.
Tina Tran, Esq. is licensed to practice law in the State of California. Please note that this answer does not constitute legal advice, and should not be relied on, as each situation is fact specific, and it is not possible to evaluate a legal problem without a comprehensive consultation and review of all the facts and court pleadings filed in the case. This answer does not create an attorney-client relationship with Tina Tran, Esq.