Deeper into forensic bias

For the recent Observer article on forensic science and the psychological biases that affect it, I spoke to cognitive scientist Itiel Dror about his work.

I could only include some brief quotes from a more in-depth exchange, so for those wanting more on the psychology of forensic examining, here’s Dror on how evidence can be skewed and why these effects have been ignored for so long.

What do you think has been the turning point for the forensic science community in terms of beginning to accept the role of cognitive bias in interpretation of evidence?

I think the clear cut scientific research with actual forensic examiners which was a within-subject experimental design, showing that the *same* expert, examining the *same* evidence, can reach different conclusions when they are affected by bias. The problem was also demonstrated in fingerprinting and DNA, very robust forensic domains.

I think you are very right to say that they have ‘began’. There has been a change, for example, the UK Forensic Regulator is now onboard. But there is still a way to go.

Which area of forensic science do you think is currently most susceptible to cognitive bias?

It will be the forensic science areas in which, as I like to say, the human examiner is the main instrument of analysis. These are most of the forensic domains: fingerprinting, DNA, CCTV images, firearms, shoe and tire marks, document examination, and so on. When there is no instrument that says ‘match’ or ‘no-match’ and it is in the ‘eye of the beholder’ to make the judgement, then subjectivity comes in, and is open to cognitive bias.

Essentially, forensic areas in which there are no objective criteria: where it is the forensic expert who compares visual patterns and determines if they are ‘sufficiently similar’ or ‘sufficiently consistent’. For example, whether two fingerprints were made by the same finger, whether two bullets were fired from the same gun, whether two signatures were made by the same person. Such determinations are governed by a variety of cognitive processes.

The cognitive nature of subjectivity is that it can be influenced and biased by extraneous contextual information. Forensic scientists work within a variety of such influences: from knowing the nature and details of the crime, to being indirectly pressurized by detectives, from seeing the ‘target’, to working within and as part of the police, from computer generated meta-data, to appearing in courts within an adversarial criminal justice system, and so on. The contextual influences are many and they come in many forms, some of which are subtle. So, many, most of the forensic areas are vulnerable.

It seems there is a reluctance to change procedures to minimise cognitive bias. Where does the resistance come from?

There are still forensic examiners who think that are immune to context and do not understand, let alone accept, the existence and danger of cognitive bias. They often confuse ‘bias’ (as in being racist, anti-Semitic etc) with cognitive bias; and this makes some of them think that it is an ethical issue. Forensic examiners rarely, if at all, receive training in this area and in the rare occasions that they do, they get bad training from people who do not specialise in providing training about cognitive bias in forensics.

The forensic community, as the military, police, and so on, are all very hard to change; there is a strong culture within those organisations. It is especially hard to promote change when errors are not as apparent as in other domains. If the police shoot an innocent person, then they very quickly know that they made a mistake, if a surgeon amputates the wrong leg, then they know very quickly that they made a mistake. In contrast, in the forensic domain, in real criminal cases, we do not know the ground truth, and do not really know if a mistake has happened or not. Only in very rare and special circumstances do errors surface (as in the Mayfield and McKie cases).

The courts have basically for the most part blindly accepted most of the forensic evidence. So, the examiners see no reason to change, if the courts accepts their evidence, then that is that. This may be changing. The hope is that judges will be more aware of the danger of cognitive bias and not accept forensic conclusions that are tainted with bias.

Link to further reading from Itiel Dror.

Interviews with interrogators

Author Dominic Streatfeild interviewed many trained military, intelligence and police interrogators for his book Brainwash and I’ve just realised he’s put the full text of the interviews online.

They’re in equal measures fascinating, disturbing and sometimes worryingly relevant, as the ‘war on terror’ still relies on many of the same physical coercion techniques used in conflicts past.

The interviewees discuss their experiences of being interrogated to being interrogators and range from being captured in the Korean War, to counter-insurgency in Yemen, to The Troubles in Northern Ireland, to the ‘war on terror’ in Afghanistan.

[Interrogation subjects in the world of intelligence tend to construct series of cover stories, like the skins of an onion. Interrogators have to] go through these stories, peeling the onion, trying to get to the core. And eventually, people run out of stories.

The interviews are:

Interview with British Interrogator #1
Interview with British Interrogator #2
Interview with British Interrogator #3
Interview with SAS NCO Trained Interrogator
Interview with Senior Royal Ulster Constabulary (RUC) officer
Interview with US Army Interrogator #1

Let slip the coins of war

A fascinating short excerpt from a new study that estimates war and population change in Ancient Rome from finds of stashed coins.

It turns out that the coin hoards are a surprisingly good guide to human behaviour:

The reasons for this correlation are not hard to fathom. People tend to hide their valuables in times of violence and danger. Emergency hoards would later be recovered by the owners unless they had been killed or driven away. As a result, the greater the intensity of warfare, the more hoards are left in the ground to be discovered by archaeologists. For this reason, the time-specific deposition rate of hoards serves as an index of internal instability caused by violent conflict and dislocation.

Coins are useful because, of course, they’re dated. So in other words, finding lots of unrecovered coin stashes from a particular time period suggests there was a lot of war.

The researchers used this measure of war intensity in Ancient Rome to estimate population changes. Neat.

Link to full text of study.

A history of ideas about the brain

Being Human has an excellent article on how ideas about the function of the brain have evolved over the centuries.

The piece is by respected science writer Carl Zimmer who wrote a fantastic book on the dawn of modern neuroscience called Soul Made Flesh.

This new article is a whistle stop tour of how our ideas about the brain have changed over the last three millennia:

For all the cognitive power that the human brain contains, it’s also exquisitely delicate. It has the consistency of custard. When an ancient anatomist decided to investigate the organs of a cadaver, he would have had no trouble pulling out the heart and manipulating its rugged chambers and valves. But after death, the brain’s enzymes make quick work of it. By the time the anatomist had sawed open the skull, he might well be looking at nothing but blush-colored goo. Who could ever think that in that goo could be found anything having to do with our very selves?

The site it’s written for, Being Human, seems to be a think tank funded social network and blogging platform for human nature geeks.

I’m not sure we need another topic specific social networking platform, most of which suffer from the fact people can’t be bothered to reconstruct the cliques they have from existing general purpose platforms (i.e. life), but it does seem to be filling up with interesting content (i.e. ideas).

Link to ‘From Cooling System to Thinking Machine’.

Hallucinations on the radio

BBC Radio 4 has just broadcast a documentary entitled ‘Hallucination – Through the Doors of Perception’ that charts the various ways in which we can experience freewheeling and autonomous perceptions.

You can hear it streamed online here or you can download it as a podcast but only for 7 more days, as like French cheese, mp3s can make you ill if they’re left out for too long.

Despite the fascinating topic, it’s actually a bit dry. It sounds like the Hitchhiker’s Guide to the Gallery without the witty commentary.

Definitely worth listening to, but probably improved by a stiff drink, or perhaps something a little hallucinatory.

Link to streamed version of hallucinations radio documentary.
Link to shortly to expire podcast page.

Feeling sheepish

Quite possibly the strangest news story I have ever come across. It starts out strange, gets stranger and then finishes on a trumpeting pageant of strangeness. From GhanaWeb:

“People who practice bestiality threaten society”-psychologist

A psychologist at the Komfo Anokye Teaching Hospital, Rev. Ekow Jackson says people who have sex with animals are potential threats to society.

He says such people have confidence problems and most times fear that their sexual advances towards humans may be turned down; a situation they cannot bear.

Such people may instead use force on the object of their sexual pleasure whether it’s a woman, a baby or an animal.

Rev. Jackson says these people should not just be ostracized or incarcerated but should be given serious psychological or psychiatric attention. He adds that some of the culprits of bestiality may have had troubled childhoods or some unresolved issues from their past.

The psychologist, who is also a minister of the Assemblies of God Church, was speaking in an interview with this reporter after a 35 year-old man, Kofi Agyeman was asked to marry a sheep he allegedly had sexual intercourse with at Wamaso in the Lower Denkyira District of the Central region.

How would we make sense of it all if there weren’t psychologists like Rev. Ekow Jackson to help us out?

Link to sheep news story.