The names change but the story is pretty much the same. "Someone else" used my Internet connection to bit torrent download a film (usually porn) illegally. The file has been deleted. I have (or don't have) a password on my router. Put another way "I got caught by a torrent tracker but deleted the file and am saying someone else unknown to me did it. Have I done enough to evade liability?" Your ISP knows. They log which subscriber had what IP address at any given time.Some ISPs use dynamic IP addressing so of course you have a different IP address now, but they know you had that IP address at that time, after all that's why they are writing you. Copyright infringement occurs when the infringing item was downloaded, and deleting it later does not eliminate liability anymore than throwing the loot in the river avoids liability for robbing a bank. Rather that only makes proof of the illegal activity somewhat harder. If you are saying that you know "someone used my Internet", you might want to change that part of your story to "I didn't do it and I don't know if anyone else did it or not." See one of the "subpoena defense attorneys" listed by the EFF and for a few hundred dollars they will likely file the needed motion to quash and copy your ISP in a timely manner. That will likely get you out of the suit, but not always. The trolls are learning and adapting and getting better at avoiding the defenses. Eventually you may have to settle, but most likely not if you use a good subpoena defense attorney. The trolls typically take the low hanging fruit, of which there is a lot, and call it good picking and leave the hard cases alone as not being economically viable. There are occasional errors in naming defendants in these torrent troll trials, and there are a few scams, as well. However, your facts most likely suggest they got you and you will need to either pay your lawyer or their lawyer. And, for the future, consider this a lesson that torrents are now being tracked and that some of the seeds are attorneys doing a sting. You might switch to streaming, but that will likely get hit next. Or, you might stop stealing copyrighted video and eliminate the problem.
Intellectual Property Law Attorney