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Our future, our universe, and other weighty topics


Sunday, January 12, 2014

The Multiverse Defendant: A Science Fiction Story

In the year 2051 the body of Ellen Taylor was found dead in her apartment, lying in a pool of blood. Two homicide detectives arrived on the scene, accompanied by their latest mobile robot, a TRM-49 unit specialized for doing work on homicides. The robot quickly took blood samples, and within 60 minutes had detected that the crime scene had blood for two different persons: the murdered woman and another person. The robot interfaced with the National Health Database to obtain a match for the second person's blood. The second person was identified as one Robert Fielding.

Homicide detectives then tried to determine the whereabouts of Robert Fielding using the citywide camera surveillance system, which had cameras on every city block. The detectives used the facial recognition system that had been introduced in the year 2040. The system told them that Robert Fielding had walked with Ellen Taylor on the streets for several days prior to the crime, and that Robert had accompanied Ellen Taylor to her apartment on the night of the murder.
 

 
The security camera system at Ellen's apartment apparently showed something similar: a man looking just like Robert Fielding entering the apartment building with Ellen. That camera system showed a man looking just like Robert Fielding running out of the apartment on the night of the murder, with blood stains on his clothes.

The police arrested Robert Fielding, and charged him with the murder of Ellen Taylor. A few months later the case came to trial. Robert Fielding pleaded not guilty.

The prosecution first presented the blood evidence. They produced a DNA expert who argued that the chance of someone else accidentally having blood matching Robert Fielding's was 1 in 1,000,000,000.

The prosecution then presented the photographic evidence. They zoomed in on the photographs, and called as witnesses facial feature analysis experts. The experts argued that the chance of someone else other than Fielding matching the face in the videos was about 1 in 500,000.

Then the prosecution called as a witness Karen Christie, a friend of Ellen who said that as Ellen was dying, she called Karen using her hologram phone and told her, “Robert Fielding stabbed me because I wouldn't have sex with him.”

Robert Fielding's lawyer did not question any of these witnesses, and called no witnesses himself. Robert Fielding was not called as a witness to defend himself.

When it came time for the closing summaries, the prosecution gave a triumphant summary, arguing that the case against Robert Fielding was the most open-and-shut murder case the court had ever seen.

Then it was the defense's turn for the closing summary. Dale Stafford, Fielding's lawyer, stood up and addressed the jury.

“This is a case about reasonable doubt,” said Stafford. “If you have reasonable doubt that my client killed this woman, you must acquit him. But you must have reasonable doubt, for a reason I will now explain.”

“Some scientists say that our universe may be only one of many universes that exist,” said Stafford. “They call this collection of universes the multiverse. Now let's imagine they're right. Let's imagine there are millions and billions and trillions and quadrillions of universes.”

“If such a thing is true, then many things that are incredibly unlikely must happen,” continued Stafford. “Even if something has only one chance in a billion trillion quadrillion of happening, we should imagine that it has happened not just once, but multiple times, assuming that there are a nearly infinite number of universes in the multiverse.”

“So let's imagine a very unlikely coincidence,” explained Stafford. “Imagine there's a country where there are two men named Robert Fielding. They both look the same, and they both have the same DNA. The chance of this happening may be one in a billion trillion quadrillion. But, in fact, such an unlikely coincidence would be likely to occur, given a sufficiently large number of universes in the multiverse.”

“So since it is perhaps likely that there could be some other Robert Fielding with a face and DNA matching my client's face and DNA,” finished Stafford, “and since that other Robert Fielding may have killed Ellen Taylor, you must have reasonable doubt that my client is guilty.”

The jury took fifty minutes to deliberate, and returned with a verdict of guilty. Robert Fielding was taken away to begin a life in prison.

After the trial as Stafford was leaving the court building, the defeated lawyer ran into one of the jurors in the elevator.

“Didn't I show there was a decent chance that some person would be wrongly accused because of some fantastically unlikely coincidence?” asked Stafford.

“Perhaps,” said the juror. “The problem was, you didn't do anything to show that this person, your client, was that some person.”

Note: this is a story of some philosophical relevance, being related to the issue of whether multiverse explanations are suitable for explaining coincidences and apparent fine-tuning in our universe.