Federal prosecutor witholds exculpatory evidence in MA. How many prosecutors are witholding evidence?

A federal prosecutor today acknowledged that she withheld evidence that could have helped clear a defendant in a gun case but said it was an inadvertent mistake and implored the chief judge of the US District Court in Massachusetts not to impose sanctions that could derail her career
"It is my mistake. It rests on my shoulders,'' a composed Assistant US Attorney Suzanne Sullivan said during an extraordinary hearing in Boston that lasted more than two hours. "I also ask the court to give me the opportunity to rebuild my reputation.''
But Judge Mark L. Wolf said he was considering several sanctions because he was so appalled by Sullivan's lapse and by what he characterized as a pattern of prosecutors in the US attorney's office withholding evidence. The sanctions ranged from fining her personally -- something prosecutors said would be a first by a federal judge in the country for a lapse of Sullivan's type -- to an order that she and perhaps all 90 prosecutors in the office undergo additional training about the constitutional duty to share such evidence.
Wolf wrote US Attorney General Eric H. Holder Jr. last month to ask him to crack down on prosecutors who fail to disclose information that could clear defendants and repeated his past assessment that the Boston office has a "dismal history of intentional and inadvertent violations.'' Wolf wrote that similar appeals he made to Holder's predecessors in recent years achieved little.

Link: http://www.boston.com/news/local/breaking_news/2009/05/us_attorney_fac.html