Portland lawyer Brandon Mayfield speaks at a press conference May 24,
2004 in Portland, Oregon. Mayfield was exonerated of involvement in
terrorist activities connected with the train bombings in Spain.
During a live Web chat in late January, National Security Agency
whistle-blower Edward Snowden explained one of the least discussed
dangers of bulk collection. By indiscriminately sweeping up the call records and the international communications
of Americans, the government has the ability to engage in retroactive
investigation, or mining the historical data of targets for any evidence
of suspicious, illegal or simply embarrassing activities. It is a
disturbing capability that should make even those fully convinced of
their own propriety to think twice before uttering out loud, “What do I
have to fear if I have nothing to hide?”
But there’s another danger that Snowden didn’t mention that’s inherent in the government’s having easy access to the voluminous data we produce every day: It can imply guilt where there is none. When investigators have mountains of data on a particular target, it’s easy to see only the data points that confirm their theories — especially in counterterrorism investigations when the stakes are so high — while ignoring or downplaying the rest. There doesn’t have to be any particular malice on the part of investigators or analysts, although prejudice no doubt comes into play, just circumstantial evidence and the dangerous belief in their intuition. Social scientists refer to this phenomenon as confirmation bias, and when people are confronted with data overload, it’s much easier to weave the data into a narrative that substantiates what they already believe. Criminologist D. Kim Rossmo, a retired detective inspector of the Vancouver Police Department, was so concerned about confirmation bias and the investigative failures it causes that he warned police officers in Police Chief magazine to always be on guard against it.
“The components of confirmation bias,” he wrote, “include failure to seek evidence that would disprove the theory, not utilizing such evidence if found, refusing to consider alternative hypotheses and not evaluating evidence diagnosticity.”
To get a better sense of the dangers, consider the case of Brandon Mayfield.
Mistaken identity
On March 11, 2004, Al-Qaeda-inspired terrorists coordinated a massive
bombing of the Madrid commuter train system during the morning rush
hour, killing 193 people and wounding approximately 1,800. Two latent
fingerprints recovered during the investigation on a bag of detonators
by the Spanish National Police (SNP) were shared with the FBI through
Interpol. When the prints were run through the bureau’s database,
it returned 20 possible matches for one of the fingerprints, one of
whom was Brandon Mayfield. A former U.S. Army platoon leader, Mayfield
was now an attorney specializing in child custody, divorce and
immigration law in Portland, Ore. His prints were in the FBI system
because of Mayfield’s military service as well as an arrest two decades
earlier because of a misunderstanding. The charges were later dropped.
Despite finding that Mayfield’s print was not an identical match to the print left on the bag of detonators, FBI fingerprint examiners rationalized away the differences, according to a report by the Department of Justice’s Office of the Inspector General (OIG). Under the one discrepancy rule, the FBI lab should have concluded Mayfield did not leave the print found in Madrid — a conclusion the SNP reached and repeatedly communicated to the FBI. The FBI’s Portland field office, however, used that fingerprint match to begin digging into Mayfield’s background. Certain details of the attorney’s life convinced the agents that they had their man. Mayfield had converted to Islam after meeting his wife, an Egyptian. He had represented one of the Portland Seven, a group of men who tried to travel to Afghanistan to fight for al Qaeda and the Taliban against U.S. and coalition forces in a child custody case. He also worshipped at the same mosque as the militants. In the aftermath of 9/11, these innocent associations and relationships, however tangential, were transformed by investigators into evidence that Mayfield wasn’t a civic-minded American, but a bloodthirsty terrorist intent on destroying the West.
But there’s another danger that Snowden didn’t mention that’s inherent in the government’s having easy access to the voluminous data we produce every day: It can imply guilt where there is none. When investigators have mountains of data on a particular target, it’s easy to see only the data points that confirm their theories — especially in counterterrorism investigations when the stakes are so high — while ignoring or downplaying the rest. There doesn’t have to be any particular malice on the part of investigators or analysts, although prejudice no doubt comes into play, just circumstantial evidence and the dangerous belief in their intuition. Social scientists refer to this phenomenon as confirmation bias, and when people are confronted with data overload, it’s much easier to weave the data into a narrative that substantiates what they already believe. Criminologist D. Kim Rossmo, a retired detective inspector of the Vancouver Police Department, was so concerned about confirmation bias and the investigative failures it causes that he warned police officers in Police Chief magazine to always be on guard against it.
“The components of confirmation bias,” he wrote, “include failure to seek evidence that would disprove the theory, not utilizing such evidence if found, refusing to consider alternative hypotheses and not evaluating evidence diagnosticity.”
To get a better sense of the dangers, consider the case of Brandon Mayfield.
Mistaken identity
Despite finding that Mayfield’s print was not an identical match to the print left on the bag of detonators, FBI fingerprint examiners rationalized away the differences, according to a report by the Department of Justice’s Office of the Inspector General (OIG). Under the one discrepancy rule, the FBI lab should have concluded Mayfield did not leave the print found in Madrid — a conclusion the SNP reached and repeatedly communicated to the FBI. The FBI’s Portland field office, however, used that fingerprint match to begin digging into Mayfield’s background. Certain details of the attorney’s life convinced the agents that they had their man. Mayfield had converted to Islam after meeting his wife, an Egyptian. He had represented one of the Portland Seven, a group of men who tried to travel to Afghanistan to fight for al Qaeda and the Taliban against U.S. and coalition forces in a child custody case. He also worshipped at the same mosque as the militants. In the aftermath of 9/11, these innocent associations and relationships, however tangential, were transformed by investigators into evidence that Mayfield wasn’t a civic-minded American, but a bloodthirsty terrorist intent on destroying the West.
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