Editor’s Note: In celebration of the last two days of Pride Month, this article briefly reflects on the immense societal and scientific contributions of Alan Turing, a member of the LGBTQ+ community.
British mathematician Alan Turing was born in June 1912. Esteemed as the father of computer science, his Turing Machine revealed the full power of modern computation, while his Turing Proof showed its limits.
At Cambridge University, Turing invented the concepts underlying modern computer software and hardware. In 1939, he joined the Bletchley Park code-breaking unit. Once there, he designed and built the automated computing machinery and algorithms needed to crack Enigma—the Nazi's coding device for sending secret wartime messages.
This innovative automated decryption helped the Allies win World War II. Intercepting coded German troop, navy and air force instructions, the Bletchley unit decoded them in time to foil enemy attacks. But the top-secret code-breaking work would remain classified for decades after the war, and Turing died before he could receive a war hero's honor and recognition.
Prosecuted in 1952 for homosexual acts, and subjected by the government to forced chemical castration, Turing took his own life two years later in June 1954 at age 41.
Jack Good, a young Bayesian statistician who worked alongside Turing at Bletchley once said, "Fortunately, the authorities did not know that Turing was a homosexual. Otherwise, we might have lost the war."
In 2009, the British Prime Minister apologized for his country's mistreatment of Turing. In 2013, the Queen pardoned the persecuted genius. In 2017, the Turing Law retroactively pardoned men for committing homosexual acts under past legislation.
While pioneering computer science, Turing also laid the foundation for modern forensic science. In cracking the Nazi's Enigma code, he introduced the likelihood ratio (LR) to measure digital information. The LR shows how much the support for a hypothesis is changed by an experiment. The LR is routinely used to measure identification information in DNA and other forensic evidence.
Advanced computer systems, like Cybergenetics' TrueAllele technology, accurately assess the impact of new evidence. Examining data, the computer measures the change in the chance that someone left their DNA. The reported LR number—Turing's Statistic—can help find, convict, acquit or exonerate suspects.
Today, in 2022, DNA evidence remains misinterpreted. Analyzed properly, informative DNA data reveals truth. But unscientific methods can relegate DNA truth to "inconclusive" silence. Better to use the best DNA science, and properly interpret evidence. Accurate LR information delivers better justice.
How can DNA analysis go wrong?
- By ignoring data, as happens when applying thresholds to DNA mixture peak heights.
- By having people manipulate DNA data input and software parameters, introducing subjective bias.
- By breaking mathematical laws, such as considering too few alternative scenarios.
Such logical errors yield inaccurate LR answers, even with some probabilistic genotyping software.
Every year, an outstanding computer scientist receives the Turing Award—the field's Nobel Prize equivalent. And, every year, crime labs choose to not use Turing's effective LR methods. They mismeasure inaccurate information on millions of DNA items. Vital evidence is lost to criminal justice.
Turing was an artificial intelligence pioneer—he proposed that a machine would pass the Turing Test when its behavior closely resembled a person’s. But in forensic science, the AI situation is reversed. Smart computers now reliably measure information on complex DNA samples. Yet only on simple DNA can a human hope to pass the Turing Test.
The world needs a new Turing Law, one that preserves and rescues DNA. When data have been ignored, or LR values are wrong, justice should demand a second look at failed DNA evidence.