Comedian John Mulaney has a joke about how easy it must have been to get away with murder before the discovery of DNA in the 1980s. It goes like this:

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Police officer: Detective, we found a pool of the killer’s blood in the hallway.

Detective: Hmm, gross! Mop it up. Now, then. Back to my hunch…

It is in this antiquated universe that Netflix’s latest psychological thriller, The Alienist, exists – though, forensic police work is not quite as limited as Mulaney suggests.

Set in 1890s New York City, the series follows the work of progressive criminal psychologist, or “alienist”, Laszlo Kreisler (Daniel Brühl), who is on the hunt for the man responsible for a number of ritualistic child murders.

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The tools at his disposal are minimal compared to the arsenal available to CSI teams today – but we do see some important elements of forensics (many not universally accepted by the police force at the time) come into play. While medical professionals were mostly kept away from crime scenes, the late 1800s were actually a turning point for the use of forensics in police investigations. So, while Kreisler has to fight to have his voice heard, he does manage to go against the will of the police department and implement processes such as fingerprinting, wound analysis and criminal profiling.

Found out about the history of these methods and how they come into play in the series below.


Wound analysis

In episode one, Kreisler asks illustrator Moore (Luke Evans) to compose a detailed drawing of the body of a young boy who was murdered. He criticises the result as being too idealistic as he is looking to understand the brutal circumstances of the murder. It is with this knowledge that the Alienist determines that the murder is connected to another case he came across in the recent past – and he later helps to clear the name of the man charged with that first killing.

Surprisingly, in-depth wound analysis was not widely practised in the late 1800s. German physician Rudolf Virchow is credited with developing a systematic method of autopsy in the 1870s, which went on to form the basis for criminal autopsies. This would not become common practise until the early 1900s – though one of the first known cases where doctors were allowed to examine victims' bodies was during the Jack the Ripper murders in London in the 1880s.

Virchow's techniques are still in use today.


Fingerprinting

In episode two, Kreisler’s young associates – twins Marcus and Lucius Isaacson – refer to “dactyloscopy: the science of a finger, palm or foot leaving a chance impression” as a new, radical method of criminal identification. Kreisler looks impressed – he has never come across it before.

The use of “finger marks” as a tool for identifying criminals came into play sometime in the late 1800s. In 1886, Dr Henry Faulds, a Scottish doctor credited with pioneering the fingerprinting system, offered his work to Scotland Yard, who declined.

The Argentine police were the first known police force to set up fingerprint files for identification purposes in 1891. It was subsequently introduced in the UK (1901) and in New York City (1902) – so the timeline in The Alienist seems about right.

According to the calculations of Sir Francis Galton, another pioneer of fingerprinting and cousin of Charles Darwin, the chances of any two fingerprints being the same are 1 in 64 billion. So, pretty reliable, then.


Identifying the murder weapon

The Isaacson brothers also manage to determine that the boy was murdered with a flashy-looking dagger called an Arkansas Toothpick, which they deemed strong enough to have caused the damage to the boy’s torso, but also finely weighted to “delicately remove his eyes”. They confirm this by using the dagger to remove the eyes from a cow at a butcher shop, and note that the wounds on its eye sockets are the same as that left on the murder victim.

Incredibly, this kind of weapon identification dates back to the 13th century and a legendary criminal court judge called Song Ci, who was active in Hunan Province in China. His book, Collected Writings on the Washing Away of Wrongs (often cited as one of the first documentations of forensic science), features an anecdote in which, in order to track down the perpetrator of a murder that was committed with a sickle, Ci got all the men in town to bring their sickles to him. After noting that one sickle inordinately attracted flies (and after testing the damage it could do to an animal carcass), Si realised he had found his killer.


Criminal profiling

Kreisler says of his plans for hunting the killer: "Though evidence does not immediately reveal him, there are hints and indications to his identity that he has unwittingly left behind. Our task is to gather those hints and indications, to construct an image of the man – his age, his background, his habits – but most importantly, his appetites. To look at who his victims are, where he commits his crimes and what exactly he does to them, until a pattern emerges."

This is a pretty succinct description of criminal profiling, a practise which is depicted – at a much more advanced stage – in another grim Netflix drama, Mindhunter.

For the advent of criminal profiling, we return once again to Jack the Ripper and the first modern profiler, police surgeon Dr Thomas Bond.

In 1888, Bond examined the investigations into the murders of four women before taking part in the postmortem of Mary Kelly – believed to be the Ripper's final victim. Bond presented medical evidence but also used his expertise to work up a profile of the murderer, describing him as "a man of physical strength and of great coolness and daring".

In doing so he helped police shape their approach to finding perpetrators.

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The Alienist arrives on Netflix UK on Thursday 19th April

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