I have traced an IP address back to the ISP, however, I cannot get the subscriber information without filing a costly civil action and obtaining a court order. I am told that I have grounds to do so, however, this has been a long process and the IP address in question is over a year old (close to 18 months). Assuming that it is not a static IP address, what are my chances that the ISP still has a record of who was using that ip? I have done searches on data retention and am left with the impression that after 3 to 9 months it is a waste of time and money.
I'm not sure if there's something on the books that require ISP's to retain IP information for certain amounts of time.
However, the IP usage will probably be kept in their daily backup. Some of those backups are not older than 2 weeks.
I agree with whomever told you anything over 3 to 9 months would be a waste of money.
However, your best option would be to hire an attorney contingent on the IP record being available at the ISP. If the attorney contacts the ISP and they don't have the IP, then you haven't spent too much money. Another alternative would be to contact the ISP yourself and just ask how long they keep the IP usage on file. You're not asking for the IP so there's no reason they shouldn't answer your question.