Thank you for the clarification. That is very helpful.
First of all, with no real evidence of any crime yet, the police won't be able or willing to help you. Your ex could simple say that the kids did it, or that he has always known that you have money. The simple fact is that the fact that you may have millions does not affect child support. Child support is based on your income, and that of the children's father---not on your respective balance sheets.
It is possible to get a subpoena for IP address history, however in order for a court to issue such as subpoena, there must be an active lawsuit on file and you must show that your request has some legal basis, and is calculated to lead to the discovery of admissible evidence.
Potential issues that you might run into are multiple users of the same IP address, even with multiple computers and other devices capable of accessing the internet---perhaps through a common wireless router.
Perhaps the most likely causes of action to file against your ex and your husband's ex are for Intentional Infliction of Emotional Distress and Invasion of Privacy. These are both intentional tort actions with the possibility of collecting not only damages to compensate you for your out of pocket expenses, but also your emotional pain and suffering as well as money damages (punitive/exemplary damages) to punish the wrongdoers.
If you can show that your ex accessed your private email account, it will not be a defense that your son gave him the password XXXXX another account that he was able to use to hack your email account. He still violated the criminal laws by doing so---both state and federal.
Here is a federal law covering this sort of wiretapping behavior, and is potentially a felony:
18 USC §2511 prohibits the interception of oral, wire, or electronic communications. The statute expressly states that any person who "intentionally" intercepts, endeavors to intercept, procures another person to intercept; or uses, endeavors to use, or procures another person to use a mechanic device to intercept any wire, oral, or electronic communication commits a punishable crime. When a device is used to intercept the electronic or wire communication, that device can be affixed to, or transmit a signal through a wire, cable, or other like connection. Also, when a device is used for the interception of the electronic communications, the person's conduct is also punishable if that person knows or has reason to know that the device has been mailed or transported in interstate foreign commerce. This statutory section sanctions the eavesdropping conduct even if "takes place on the premises of any business or other commercial establishment the operations of which affect interstate or foreign commerce; or obtains or is for the purpose of obtaining information relating to the operations of any business or other commercial establishment the operations of which affect interstate or foreign commerce." It is also a crime to "intentionally" disclosing, or intending to disclose, the intercepting communications to any other person; this is particularly applicable to spouses that intent to use the eavesdropped e-mails in family courts. This crime carries fines or imprisonment for up to five years. In certain circumstances, usually involving more serious violations, the person may be civilly sued by the Federal Government.
As soon as you have gathered the evidence of his illegal behavior that will support your civil suit, the same proof can be used by the local state prosecutor to file criminal charges.
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