“When you have eliminated the impossible, whatever remains, however improbable, must be the truth” - Sherlock Holmes.
Wrong! - You can never know all other options, and you can never know they are impossible.
In 1999, Sally Clark was convicted of murdering her two sons and was jailed for life. She served three years before being released on appeal in 2003. The expert testimony of Pediatrician Professor Sir Roy Meadow was instrumental in this conviction, as it was in the conviction of Angela Cannings, Donna Anthony and Trupti Patel for murdering their two, two and three children respectively. These three women were also eventually freed on appeal.
The children died due to Sudden Infant Death Syndrome (SIDS), known as cot death in the UK. But Meadow testified for the prosecution that the odds of a child dying from SIDS were 1 in 8,543, and so the odds of two children from the same family dying from SIDS were 8,843 squared – or 1 in 72 million. The jury bought the idea that these odds were so astronomical the mothers must have murdered their children.
Anyone with a basic knowledge of logical fallacies would recognize this as a false dilemma – a limited number of options (usually two) are given, while in reality there are more options. Let’s suppose the odds of two children dying from SIDS by pure chance really are 1 in 72 million. Meadow and the jury made the mistake of assuming there were only two choices – chance or murder. They ruled out chance so it must be murder, right? Wrong, because there are at least two other options, for example: a genetic pre-disposition; or something in their home. There are probably others we don’t know about because you can never know all other options. It wasn’t chance that these children died, but that didn’t mean it was murder.
Critical thinkers would also note that no positive evidence was offered for murder, just negative evidence against SIDS. If you want to prove something true you must actually prove it true, not just claim that all alternatives are impossible, because you can never know all other options are impossible. This reversal of the burden of proof is a fallacy known as argument from ignorance - unless something (murder, in this case) has not been proven false, it must be true.
It’s mind-blowing that a jury didn’t see these logical errors, unbelievable that the defense attorney didn’t make the case for them and disgraceful that a prosecution could even be brought with such flimsy evidence. It gets worse - Meadow testified in the Patel trial after the law lords had already called his same evidence in the case of Cannings and Clark, “grossly misleading”. How did this happen? Meadow, with his long list of qualifications, was considered an authority on the subject, and prosecutors and jurors were in awe of him. And this neatly illustrates a third fallacy, argument from authority - even experts can be wrong; what counts are the data not the qualifications of the person presenting them.
Meadow is currently facing a General Medical Council hearing into charges of serious professional misconduct. Last week it heard he gave "misleading and flawed" evidence in Clark’s trial. He could be struck off if found guilty.
A key tool of critical thinking is to know and understand logical fallacies: don’t rely on them yourself and recognize them in opposing arguments. It seems to me the application of critical thinking and recognition of fallacious reasoning in these cases could have prevented these innocent women from going to jail.
As for Sherlock Holmes, despite his reputation he really wasn’t much of a critical thinker. But that shouldn’t be too surprising: his creator believed in fairies at the bottom of the garden.