> Does anyone know of a reliable source that can help me verify some  
> of these titles?

I'm sure Jessica Rosner is correct that no 100% reliable list exists.  
But how reliable you need your info to be depends on your purpose.

If it's a research question: you want to write about films that have  
fallen into the public domain, you would certainly be able to discuss  
films that appear on several lists, with attribution: e.g. 'while  
definitive information on copyright status is often elusive, and some  
works can be brought back into copyright, these works are widely  
considered to now be in the public domain.'

If, on the other hand, you want to DO something with the films: show  
them, use bits of them as examples, or make found footage art out of  
them, you probably have little to worry about anyway because: 1) your  
purpose might be covered by Fair Use anyway, 2) as an academic you're  
not really worth suing -- the attorneys have much bigger fish to fry.

Either way, a few things one might do to find out more about what is  
and isn't PD.

Check the catalogs of Alpha Video and other distributors of ultra- 
cheapo DVDs. I think all their titles are PD, especially anything that  
has come out from several different distributors (e.g. Meet John Doe).  
First, anything that is being distributed in this manner is  
functionally PD, and second if some copyright holder shows up they'll  
be going after these distributors, not anything you might have done  
with the films.

If you have questions about specific titles that appear on one list or  
another, especially for shorts, docs, industrials... check The  
Internet Archive. Anything there is generally labeled with pretty  
accurate rights info.

Finally, you can check the work of the Orphan Film people, Dan  
Streible at NYU, and the programs of the Orphan Fiulm Symposiums. The  
Orphan Film concept being works that are still in copyright but have  
been abandoned or whose rights holders cannot be identified, the  
'Orphanistas' have pretty good info on what's PD, and what's just in  

Screen-L is sponsored by the Telecommunication & Film Dept., the
University of Alabama: http://www.tcf.ua.edu