"The most expensive part of e-discovery is attorney review," Palumbo says. "If you don't cull those data files down a long way you end up handing them off to associates to go through them, and at $200, $300, $400 dollars an hour, that adds up pretty quickly. "

Palumbo uses an on-premise version of software from that automates much of the process of filtering the data.

First to go are the system files, .jpeg files, audio files and others that are clearly inappropriate. Next are those of the right type but wrong date. Then he can contact the lawyers on the case, to further identify which files are relevant.

At that point the 100GB file may be down to 80GB, at no cost to the client. An outside firm would charge about $350 per GB for that service, he says. More complex filtering, based on content, costs far more: Outside service bureaus typically charge about $1,000 per GB for full filtering and reduction, Palumbo says. Typically, Foley Hoag will do the simple level of filtering at no cost to clients, though it charges for more complex parsing and reduction.

With an updated list of data custodians, Palumbo uses the Clearwell system to filter documents by time and e-mails by sender or recipient, then a combination of e-mail domains, keywords and boolean conditional searches.