July 20, 2024


Science It Works

CrimeCon 2022: Forensic Scientist Dr. Henry Lee On Logic

Renowned forensic scientist Dr. Henry Lee spoke at CrimeCon 2022 to discuss the importance of logic in the criminal investigation process.

Lee’s work has taken him around the world, assisting law enforcement agencies in closing more than 8,000 cases over the span of his 50-year career. His expertise has been valuable in some of the highest-profile cases in history, including O.J. Simpson and JonBenét Ramsey.

He currently stars in the streaming series “Trace Evidence: The Case Files of Dr. Henry Lee.”

“I never dreamed, in my life, how my work could affect the world,” he told the Las Vegas audience.

Lee lectured through a presentation featuring slides with real-life photos from crime scenes, asking the audience varying questions about their observations. In one image, guests observed the body of a woman believed to have been jogging in the park when someone stabbed her 11 times.

Dr. Lee pointed out the woman wasn’t wearing underwear, asking CrimeCon attendees how many enjoyed jogging without wearing underpants.

“Logic is important,” he said.

Dr. Lee explained that three kinds of logic should be applied to studying crime scenes: Inductive, deductive, and abductive.

“Of course, Sherlock Holmes says it is elementary,” said Lee. “But logic is not elementary.”

Dr. Lee provided examples of each type of logical reasoning, noting how each one contains three factors: precondition, conclusion, and a rule. Each type of logic depends on the ordering of those factors:

Induction: “When it rains, the grass gets wet. Therefore, if it rains tomorrow, the grass will get wet.”

Deduction: “When it rains, the grass gets wet. It rained today. Therefore the grass is wet.”

Abduction: “When it rains, the grass gets wet. The grass is wet. Therefore, it may have rained.”

“However, with forensic work, you have to justify the place, the time,” Lee said. “For example, I’m playing golf. [The] grass [is] wet. It’s not raining. Why? Because [the] sprinkler[s] get the grass wet. At the crime scene, it’s the same thing.”

The audience laughed when the slide featured a photo of the witty doctor playing golf.

To support his statements, Dr. Lee reexamined his work on the case of Elizabeth Smart, who was abducted from her Salt Lake City, Utah, home in the middle of the night back in 2002. When approaching the house, Dr. Lee had to examine each point of entry that Smart’s abductor could have used, including the chimney.

“Observation. Ok, someone can get to her bedroom to kidnap her. What [does] logic tell us? You have to get into her house, right? How to get into the house? Process of elimination,” said Dr. Lee. “When you eliminate all the impossibles, whatever remains becomes more probable.”

When Dr. Lee couldn’t reach where Smart’s abductor cut through a screen window, he determined the assailant had to be tall and thin. And based on the location of the Smart home atop a hill, he concluded the kidnapping wasn’t random.

These deductions would prove to be true when Elizabeth Smart was rescued from her captors in March 2003.

“[In] this case, we did not do any sophisticated forensic analysis, just logic,” said Dr. Lee. “So everybody here, you can solve a case just using your mind and [by] analyzing.”   

Dr. Lee is the founder of The Henry C. Lee Institute of Forensic Science and the University of New Haven. For more, you can visit his Facebook page here.

CrimeCon 2022 is produced by Red Seat Ventures and presented by Oxygen.

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