A Washington-based FBI agent whose alleged heroin use has prompted the dismissals of cases against 28 drug defendants, was himself charged Friday in federal court.

Prosecutors allege Matthew Lowry, 33, of Upper Marlboro, Md., repeatedly checked seized heroin out of an evidence room for his own use, cut it with Creatine and laxatives to hide the missing amounts and returned it while forging signatures and evidence labels.

His lawyer, Robert C. Bonsib, said Lowry has been cooperating with the Justice Department investigation since his crimes were discovered and intends to plead guilty at an upcoming court hearing.

Prosecutors estimate he will face a minimum of more than 7 years in prison.

"Mr. Lowry recognizes the importance of taking full responsibility for each of his acts," Bonsib said in a statement. "He also recognizes the need to account to the public for his misconduct."

Although none of Lowry's alleged crimes occurred in Philadelphia, the case is being handled by the federal prosecutors from here because Lowry worked on several drug cases later prosecuted by the U.S. Attorney's Office in Washington.

Lowry was charged with 20 counts of obstruction of justice, 18 counts of falsification of records, 13 counts of conversion of property and 13 counts of heroin possession.

According to court filings, Lowry also participated in several undercover heroin buys and failed to check the government-financed drugs into evidence.

He was suspended in September, after being found incoherent after a heroin overdoze under a crane in the Washington Navy Yard. That threw several long-running drug investigations into disarray.

So far, federal judges have dismissed cases against 28 defendants, some of whom had pleaded guilty and been sent to prison, and ordered federal prosecutors in D.C. to notify more than 100 others that Lowry participated in the investigations that lead to their arrests.

In his statement Friday, Bonsib said his client became addicted to heroin while trying to kick an addiction to pain medication he had been prescribed for a colon condition.