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Perfect crime

Perfect crime is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Perfect crime rather than just read about it. In short: A perfect crime is a crime that is undetected, unattributed to an identifiable perpetrator, or otherwise unsolved or unsolvable. The term is used colloquially in law and fiction (especially crime fiction) for both crimes committed as crimes foremost, and those committed as a kind of technical achievement on the part of the perpetrator.

Key takeaways

  • Perfect crime belongs to science; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Perfect crime to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Perfect crime from memory before moving on to harder problems.

Reference excerpt

A perfect crime is a crime that is undetected, unattributed to an identifiable perpetrator, or otherwise unsolved or unsolvable. The term is used colloquially in law and fiction (especially crime fiction) for both crimes committed as crimes foremost, and those committed as a kind of technical achievement on the part of the perpetrator. The term perfect crime connotes one that is (or appears likely to be) unable to be solved, which distinguishes it from one that has merely not yet been solved, or where everyday chance or procedural matters frustrate a conviction. In certain contexts, such as a poisoning, some argue the bar must be raised to where the mere detection of a crime having been committed renders it imperfect.

Overview As used by some criminologists and others who study criminal investigations (including mystery writers), a perfect crime goes unsolved not because of incompetence in the investigation, but because of the cleverness and skill of the criminal. Would-be perfect crimes are a popular subject in crime fiction and movies. They include Perfect Crime (play), Rope, Double Indemnity, Special 26, Strangers on a Train, The Postman Always Rings Twice, Witness for the Prosecution, Dial M for Murder, Don 2 and Aaryan.

Varying definitions A murder committed by somebody who had never before met the victim, has no criminal record, steals nothing, and tells no one might be a perfect crime. According to criminologists and scientists, this casual definition of perfect crime exists. Another possibility is that a crime might be committed in an area of high public traffic, where DNA from a wide variety of people is present, making the sifting of evidence akin to 'finding a needle in a haystack'. An intentional killing in which the death is never identified as murder is an example of one of the more rigorous definitions of perfect crime. Other criminologists narrow the range to only those crimes that are not detected at all. By definition, it can never be known if such perfect crimes exist. Many "close calls" have been observed, however—enough to make investigators aware of the possibility of a perfect crime.

Unprosecutable crime

In 2005, Professor Brian C. Kalt of Michigan State University College of Law put forth an argument that the Vicinage Clause of the United States Constitution – requiring jury selection from the population of the state and court district where the crime is committed – may permit the commission of the "perfect crime" on the technical grounds that a jury trial could not be carried out. Since there are no residents in the portion of Yellowstone National Park that lies within the state of Idaho, and since the entire park has been placed within the jurisdiction of the United States District Court for the District of Wyoming, there are no residents available to form a jury for crimes committed in this specific "Venn diagram" location. Similar rationale contributed to the dissolution of Bullfrog County, Nevada, in 1989; because the county was unpopulated, and was not assigned to a judicial district, criminal trials could not legally be held there under Nevada state law.

Real-life examples In March 2009, a $6.8 million jewel theft in Germany was described as being close to a perfect crime, in that despite having DNA evidence (but no other evidence), the police were unable to bring the case to court since the DNA belonged to one of a pair of identical twins, and faced with denials by both, it could not be proven which of the two was the criminal. Other examples of one, or possibly both, identical twins avoiding punishment include juries unable to reach a verdict in a 2004 Boston rape trial, a 2005 Houston rape trial and a 2009 Malaysia drug-smuggling trial. The infamous 1987 Opera House heist in India by a group of men impersonating CBI officers was described as a perfect crime.

See also Locked-room mystery Leopold and Loeb Population Zero, a 2016 feature film with the Vicinage Clause as the central plot device Category:Unsolved murders

References

Further reading Timmermans, Stefan (2007). Postmortem : how medical examiners explain suspicious deaths. University of Chicago Press. ISBN 978-0-226-80398-2. OCLC 1024141852. Jekel, Pamela (1982). The perfect crime and how to commit it. Paladin Press. ISBN 0-87364-237-6. OCLC 7944812. Gardner, Ross M (2005). Practical crime scene processing and investigation. CRC Press. ISBN 0-8493-2043-7. OCLC 730237900.

External links "Horizon – How to commit the perfect Murder". BBC TV/Radio. 2007-04-10. Retrieved 2019-09-05.

Worked examples

Example 1 — a first encounter with Perfect crime

Start with the simplest possible case. Write down what Perfect crime claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Perfect crime before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Perfect crime ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Perfect crime

In research
Perfect crime appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Perfect crime in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Perfect crime is common in secondary-school and first-year university syllabi. It links to neighbouring topics Crimes, Criminology, so understanding it makes those chapters shorter.
In everyday life
Look for Perfect crime outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.
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How to study Perfect crime in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Perfect crime means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Perfect crime out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Perfect crime in simple terms?

A perfect crime is a crime that is undetected, unattributed to an identifiable perpetrator, or otherwise unsolved or unsolvable. The term is used colloquially in law and fiction (especially crime fiction) for both crimes committed as crimes foremost, and those committed as a kind of technical achie…

Why does Perfect crime matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Perfect crime?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Perfect crime.

Tags

  • Crimes
  • Criminology

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