Photographs from FBI files of the Chevrolet Impala, which had been assigned to FBI agent Matthew Lowry, in which heroin and other evidence was found. Some area were redacted by court officials to prevent disclosure of sensitive information. (U.S. District Court)

FBI agent Matthew Lowry checked out Item 1B4 from the evidence room at the bureau’s Washington field office on an August morning in 2013. He wrote “to lab” on a log sheet to explain why he was taking drugs that had been seized in an undercover operation dubbed Midnight Hustle.

But it was nearly a year later when he delivered the drug package to the lab. For 10 months, court records show, the heroin had gone unaccounted for and unmissed. When the package made it back to the FBI office in September, it weighed 1.1 grams more than when it had been seized.

Someone had tampered with the contents, prosecutors said later.

The package is one piece of a tale that has unfolded in recent months — the case of an FBI agent who, by his own admission, repeatedly stole heroin from evidence bags for his personal use. In the process, he sabotaged drug cases that he and his colleagues had labored on for months. Prosecutors have dismissed charges against 28 defendants in three cases, many of whom had already been convicted, and they say it could affect 150 other defendants.

The revelations have exposed a system of weak checks and balances that allowed Lowry’s thefts and drug use to go undetected for at least 14 months as he worked on a task force focusing on heroin traffickers along the borders of the District, Maryland and Virginia. The problems were discovered only after the agent disappeared after work Sept. 29 and was found by colleagues incoherent, standing next to his disabled bureau car in a construction lot near the Washington Navy Yard.

A look at how Agent Lowry affected the case of Earl Owens, who was eventually dismissed.

FBI documents say the agency vehicle, which had run out of gas, was littered with bags of heroin “sliced open and drugs removed,” along with a shotgun and a derringer pistol seized during a drug raid but never logged into evidence.

An examination of court records and more than 600 pages of internal FBI documents obtained by The Washington Post — including statements Lowry made to investigators describing his actions — provides a detailed look at his elaborate deception and downfall. The case has prompted an exhaustive review of how drug evidence is handled in one the largest and most prestigious of the bureau’s 56 field offices.

“It’s shocking that there was such little oversight,” said Steven H. Levin, a private lawyer in Baltimore with 10 years’ experience as a federal prosecutor, much of it overseeing the violent-crimes section in Maryland. “It’s something you would expect to see on a made-for-TV movie. . . . You’re thinking, there is no way that could ever happen. And that’s what happened.”

Lowry, 33, remains the target of a criminal investigation that is being led by federal prosecutors in Pennsylvania to avoid any conflict of interest. He has not been charged with a crime, but he was suspended from his job and entered into drug counseling immediately after he was found in September. His attorney, Robert C. Bonsib, declined to comment for this article, but he has said his client is cooperating with authorities. In the documents, which were provided to defense attorneys in the drug cases under review, Lowry said that he turned to heroin after becoming addicted to prescription painkillers because of an illness and that he started taking heroin from evidence in the summer of 2013.

A spokesman for the FBI’s Washington field office, Andrew Ames, issued a statement saying protocols for handling evidence are being tightened. “The incident has brought to light certain vulnerabilities the office is addressing to reduce the likelihood of this type of misconduct happening again.”

Levin said Lowry’s conduct “should have raised questions right way.” He added, “How many people share blame for allowing this to be perpetrated, and for it to continue for as long as it did?”

The system

Lowry’s system was basically quite simple, according to the FBI documents and a summary of his statements to investigators, in which he told them how he took drug evidence from cases with code names including Broken Cord, Family Matters, Tequila Shot and Smellin Like a Rose.

Photographs from FBI evidence files of heroin found in the car assigned to FBI agent Matthew Lowry. Prosecutors dropped drug cases against 28 defendants in four cases based on evidence now deemed tainted. (U.S. District Court)

He checked out drugs from cases he had worked on the pretense of taking them to a lab to be tested for trial. He kept the drugs — sometimes for days or weeks, other times for months — and used a little bit nearly every day, he told investigators. He eventually submitted the drugs to the lab and took them back to the FBI office when testing was done.

Lowry described for investigators a painstaking process used to circumvent rules and procedures and avoid detection, court documents state. He said he forged signatures of supervisors to authorize withdrawals and of colleagues to reseal evidence bags he had cut open, taking time to practice the signatures. He often targeted cases that were already resolved, making it less likely another agent would need the drugs and notice that evidence was missing.

Lowry told investigators he routinely used a filler to repackage bags of heroin. He said he often added an over-the-counter laxative but also used creatine, a chemical commonly mixed with heroin before it hits the street. An FBI memo said Lowry used a digital scale — taken from a drug house — to ensure that he repackaged the drugs at close to their initial weight.

An agent told investigators that Lowry had “stated that the ‘system was messed up’ and that ‘anybody can check out anything,’ according to the court papers..

The 21.3 grams of heroin Lowry took from the Midnight Hustle evidence had been bought for $1,800 by an undercover FBI agent in a June 2013 street deal on Rhode Island Avenue NE in the District, according to the court papers. Lowry checked out the drugs two months later. The FBI documents say he broke the evidence seal on the bag and kept the drugs in the trunk of his Chevrolet Impala, where he stored it “between uses.”

On June 30, Lowry took the drugs to the lab, according to the documents. He added Purelax, a powdered laxative, “to offset the weight of the drugs he used,” the documents state. He obtained a new evidence bag and an evidence seal. He forged the signatures of the two agents who had seized the heroin the previous year, and he tried “to mimic the hand-writing on the original sealing sticker,” the documents state.

Lowry peeled a bar code off the original evidence bag, put it on the new bag and then sealed the bag with heat. He told investigators that he didn’t sign the same drugs out twice because he recognized the forged signatures as his handwriting. A few times, he took guns, drugs or other items from crime scenes and did not log them into evidence.

One agent interviewed by investigators said that “drug evidence is controlled very tightly, as you guys know. There’s very stringent rules on how you handle it. They’re pretty robust.” But, the agent said, “if somebody is actively trying to subvert the process, then they can defeat the rules. And that’s apparently what happened in this case.”

A high error rate

An internal audit by the FBI, completed last month, found that every one of the nation’s field offices had problems tracking gun and drug evidence and that in some cases, drugs disappeared for months without notice. The Washington field office was among those with the highest error rates; 90 percent of drug evidence examined had been mishandled or had record-keeping problems.

In the Washington field office, a single agent could check drugs out of the lab, even from cases the agent had not worked. All that was needed was a supervisor’s signature. When an agent is taking drugs to a lab, protocol dictates that the trip is made immediately, with no stops. But two senior law enforcement officials interviewed said no one checks to ensure that the packages are dropped off. It can take months or even a year for evidence to be tested, so it’s not unusual for packets of cocaine or heroin to be gone for long periods of time. Also, the Washington field office is one of the few in the country whose agents take drugs to the lab in their cars.

One FBI official said small variations in the weight of drug evidence after testing are often a result of repackaging. Supervisors are supposed to review agents’ quarterly log sheets, documenting progress on investigations and listing drugs signed out from labs. It is unclear whether Lowry’s log sheets were thoroughly reviewed.

As a result of the case, the Washington field office “is re-examining certain policies and processes for how drugs are checked out, transported, tracked and checked into the lab,” according to a senior law enforcement official who discussed the case on the condition that he not be identified because of rules that forbid publicly discussing pending criminal cases.

In one significant change, two agents will be required to check out evidence, the official said, describing what is considered a best practice. That exceeds requirements in place across the entire bureau.

Michael Bromwich, a retired inspector general with the Justice Department, said even when strict controls are in place, compliance can weaken over time. Requiring two agents to sign out drugs, for example, “is an administrative burden.” He said, “I think that over time the controls begin to loosen. It never occurs to them that somebody would make off with the drugs and steal the money.”

Cases upended

The Lowry investigation has stunned police and prosecutors, upended their cases and returned men who had admitted or been convicted of felony drug crimes to the streets of the District and Maryland.

Assistant U.S. Attorney Darlene Soltys told a federal judge how hard she worked to “salvage” a drug case Lowry had worked. “My agents invested their hearts and souls in investigating this case,” she said during a closed-door hearing in a judge’s chambers. The transcript was recently unsealed.

In that hearing, Soltys meticulously explained Lowry’s role in the search of an apartment from which 2.2 pounds of heroin was seized. It was a stash and packaging house for drugs, with “powder everywhere,” authorities said.

Lowry and another agent moved together through the apartment, with Lowry hanging evidence signs and the other agent taking photographs. The procedure is intended to ensure that no one is alone with evidence. “They moved from room to room to room,” Soltys said. But she said agents could not conclusively testify that Lowry was never alone.

It appears that nothing was taken or tampered with during that search, the prosecutor told the judge. But FBI agents also searched the same defendant’s house in Accokeek, in Southern Maryland, where they reported finding expensive watches and jewelry, two guns, and $780,000 in cash split into bags. Soltys said the bags were brought to Washington, and Lowry was among the agents who helped recount the money. The prosecutor said authorities initially thought that one bag was missing and that the final count was $130,000 short.

It was determined later, after the case had been dropped, that an honest miscount of the money had occurred, but as investigators sorted through the stolen drug evidence, the count became suspect. Just the suspicion of misconduct tainted the case.

“So now, I can no longer demonstrate the integrity of the money that was seized,” Soltys said in the hearing. Pressed by the judge, she said that evidence in the case gathered at three locations ended up spread out in an office where Lowry and others worked.

Soltys told the judge that because Lowry “is going to be portrayed as a heroin junkie” and as “drawn to that heroin like moth on a flame,” she could not at the time vouch for the money they thought was missing. “Can anybody say that they had their eyeballs on the evidence that we brought back from the safe house?” she said.

She added, “The integrity of my prosecution is undermined by the presence of this bad agent.”

The prosecutor told the judge that “it is not a question about saving the FBI the embarrassment. They’re already embarrassed by this. The question is, can I, on behalf of the United States of America, stand up and argue to a jury that my evidence is pristine, that there is any doubt that my agents are credible?”

Charges against four drug defendants in the case were dismissed.

Sari Horwitz contributed to this report.