In September and October 2001, at least five envelopes containing Bacillus anthracis (anthrax) were mailed to Senators Patrick Leahy and Thomas Daschle and to members of the media in New York City and Boca Raton, Florida. The specific strain which infected individuals was known as Ames – it was isolated in Texas in 1981 and transferred to the United States Army Medical Research Institute of Infectious Diseases (USAMRIID). No other natural outbreak of Ames has ever been recorded.

After the bioterrorist attacks were identified, the Federal Bureau of Investigation (FBI) and the United States Postal Inspection Service (USPIS)formed a task force to investigate the crime. The Investigation lasted seven years and was undertaken by FBI field offices in Miami, New York,Newark, New Haven, Baltimore and Washington,D.C. At the beginning of the investigation,the limitations on scientific analysis prevented the task force from finding the culprit because it was impossible to determine precisely which spores the anthrax came from.

Early investigative efforts focused on genetically classifying the spores and tracking the envelopes used in the attack. However, it was slow going because the laboratory tests required to analyze the spores had to be created and subsequently validated. Furthermore any traditional forensic protocol for examining evidence was difficult since the letters were contaminated.

While the tests were being developed, validated and implemented, the FBI created likely profiles of the offender(s), which included scientific ability, access to the Ames strain, proximity to where the letters were mailed, any suspicious behavior,public tips and motive.

At first, Dr. Steven J. Hatfill became a person of interest because people came forward who suspected that he might be involved. Dr. Hatfill worked for USAMRIID from 1997-1999and had unrestricted access to the Ames strain. In 2001, Dr. Hatfill had filled multiple prescriptions for Cipro, the only U.S. Food and Drug Administration (FDA) approved drug to treat anthrax. In addition, he was well versed in the intricacies for dispersing anthrax via mail. However, the Cipro was also consistent with treatment of an infection Dr. Hatfill had at the time and knowledge of anthrax dissemination was commonplace among those in the bio-defense community of which Dr. Hatfill was a member.

In 2007, after scientific spore analysis was developed specifically for the case, it was established that RMR-1029 was the parent material to the anthrax used in the attacks. This exculpated Dr.Hatfill as he never had access to the bio-containment suites at USAMRIID that held RMR-1029, meaning he never could have obtained the specific spore batch used in the anthrax attacks.Eventually the FBI settled with Dr. Hatfill for $4.6 million.

This discovery helped narrow the search to those who were at the USAMRIID lab where RMR-1029 was stored between September 11and 18, 2001 and October 1 and 8, 2001. Interviews,polygraphs, laboratory notebooks and records analysis, home and computer searches,and other investigative efforts established Dr.Bruce E. Ivins, who worked at the USAMRIID, as a person of interest.

According to the FBI report, Dr. Ivins was alone in the lab late at night and on the weekends immediately preceding when the letters were mailed. He had never before exhibited this work pattern, never did so after the attacks and was unable to give a legitimate explanation for why he kept those hours. Also, as the investigations continued, the investigators found that Dr. Ivins Suffered from psychological problems.

The investigation was undertaken in a covert manner until the fall of 2007. At that point,agents obtained search warrants for his home,cars and office. On November 1, 2007, the FBI searched his property and found 20 years of letters Dr. Ivins had sent to Congress and the news media, three handguns, two stun guns, a taser and other suspicious items.

On July 12, 2008, Dr. Ivins’ home was again searched because he had made threats in a group therapy session. They found a bulletproof vest, a homemade reinforced body armor plate, hundreds of rounds of ammunition and handgun powder. In addition, the investigation noted that Dr. Ivins had boasted about his ability to create highly pure batches of anthrax.

The investigation concluded that Dr. Ivins had the opportunity, motive (based on e-mails and statements to friends), mental health problems,proximity to where the letters were mailed, a similarity in language to the letters, consciousness of guilt (he decontaminated his office and failed to report it), an inability to explain his behavior when confronted with evidence, and obsessive behavior. During the investigation, it was found that, dating back 40 years, Dr. Ivins had been obsessed with the Kappa Kappa Gamma(KKG) sorority. Many times, he would drive several hours to visit various sorority chapters. The letters were all mailed outside of an office building that housed a KKG sorority.

In the summer of 2008, authorities began toseek an indictment charging Dr. Ivins with theuse of a Weapon of Mass Destruction. Before hewas charged, Dr. Ivins committed suicide. Theinvestigation concluded by confirming that Dr.Ivins was the guilty party.

At least 22 victims contracted anthrax, with five people dying from the infection. In addition, 31people tested positive for exposure to anthrax spores and 10,000 more people were deemed at risk from possible exposure.

In all, 35 post offices and mail rooms were contaminated along with seven buildings on Capitol Hill in Washington, D.C.

The investigation included over 600,000 investigator hours, 10,000 witness interviews, 80searches and over 6,000 pieces of evidence. In addition, there were 5,750 federal grand jury subpoenas issued and 5,730 environmental samplescollected from over 60 sites. The investigationcost $100 million.

Nevertheless, the investigation never producedreal forensic evidence that proved how Dr. Ivinsmade the spores and weaponized them

.While Dr. Ivins had access to RMR 1029, someco-workers said that others at the facility or potentiallyeven outside visitors could have had accessto the stock.

In July, 2011, Justice Department lawyers filedcourt papers that said Dr. Ivins lacked access tothe equipment required to actually produceweaponized powder.

Justice Department civil lawyers wrote in a July15 filing that “the sealed area in Bruce Ivins’ labdid not contain the equipment needed to turnliquid anthrax into the refined powder thatfloated through congressional buildings andpost offices in the fall of 2001.”

However, just four days later, Justice Departmentlawyers revised the filing to say Dr. Ivins merelylacked access in his specific lab to the requiredequipment, noting that the filing should havesaid, “while the Army lab did not have alyophilizer, a freeze-drying machine, in thespace where Dr. Ivins usually worked, there was a lyophilizer and other equipment in the building that he could have used to dry the anthraxinto powder,” according to the New York Times ina July 19 story.

In its revision, the Justice Department contendsthe original filing was mistaken and Dr. Ivins hadaccess to the equipment at the facility.

According to Justice Department SpokesmanDean Boyd, as noted in a ProPublica story onJuly 20, the government has “never waveredfrom the view that Dr. Ivins mailed the anthraxletters