Downloading torrents from public wifi

First, let me set the context for you. I've downloaded three or four old (but no doubt still under copyright) movies (ex.: The Love War, a 1970 Lloyd Bridges/Angie Dickinson movie). Over the past few years I've also downloaded or torrented probably 12 or 13 albums of obscure 1950s-1970s music, and a few episodes of older TV shows while on the road in hotels.

Last week, a guy in my city was busted for what was evidently an unusually large cache of illegal pornography; and today, Lifehacker had a long, interesting article on illegal downloading. Together, these things got me thinking.

I know law enforcement can track you down in your own house (as I gather it, they would subpoena an ISP to show them your records). But what if you're using a public access point, like a coffeeshop, public library or the hotels I've stayed in? Or even a neighbor's open wifi? Could they still trace you somehow?

Note that I wouldn't do this -- for all I know, my neighbor has a data cap and I wouldn't want to bust it. I'm just wondering about the mechanics of it. Can law enforcement trace your individual computer through someone else's open wireless connection?

Asking anonymously because I don't want to hear from Angie Dickinson's lawyer.