"Jack the Ripper" had no modus operandi

The argument

Serial killers are almost always compulsive killers with very strong tendencies to commit their crimes in particular ways. The modus operandi of a killer is defined by the specific methods and behaviors exhibited during their murders, but Jack the Ripper had no apparent modus operandi. This matters as evidence because consistency is not incidental to such crimes; it is held to follow from the compulsion driving them, which is why investigators treat a repeated method as the signature linking one case to another. Instead of a single consistent pattern of killing, the Ripper murders were committed in a variety of different ways. The Ripper's first canonical victim, Polly Nichols, had her throat cut and her body wounded, but the next victim, Annie Chapman, was disemboweled. Catherine Eddowes was killed by a small incision to the throat, but the final victim, Mary Kelly, was savagely mutilated. The variation runs in both directions rather than along a single line, which is the detail that tells against the usual explanations. A killer's method may develop over time, so an escalating series might be attributed to one person; but these differ from each other in kind and not in degree, and the sequence does not progress. What links the canonical cases is therefore mainly the place and period in which they occurred. No single method of killing links the Ripper's victims together, indicating that the "Ripper" was not a single individual. On this argument the figure of Jack the Ripper is a construction after the fact — several unconnected killers in the same district over a short span, gathered under one name because the crimes were reported together, rather than one man with a pattern that cannot be found because it was never there.

Premises

Counter-arguments

The premise that serial offenders keep a fixed method is the reverse of what investigators working on these cases hold. Method is learned behaviour: it adapts to circumstance, opportunity, interruption and growing confidence, which is why analysts distinguish it from signature — the elements an offender repeats because they are the point of the crime rather than the means of it. Variation across a series is expected, not anomalous. The specific variation described also has a straightforward explanation in the circumstances. The earlier killings occurred outdoors, in streets and yards where the offender had minutes at most and risked discovery at any moment; the final one occurred indoors, in a private room, with hours available and no risk of interruption. The extent of the mutilation tracks the time available almost exactly, which is what one would expect of a single offender constrained by his surroundings rather than of four unrelated killers. The claim that no method links the victims is not sustained by the account itself, which describes throat wounds in more than one case and abdominal injury in more than one. What links them is more consistent than the argument allows. And the alternative it proposes is the less economical one: several killers operating independently in a few streets over a few months, none of whom continued afterwards.

Rejecting the premises

[Rejecting P1] Investigators distinguish method — which adapts to opportunity, interruption and experience — from signature; variation across a series is expected rather than evidence of separate offenders. [Rejecting P2] The account itself describes throat wounds in more than one victim and abdominal injury in more than one, and the escalating mutilation tracks the time and privacy available at each scene.