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The Sad But True Case of Earl Washington

DNA Analysis and the Criminal Justice System


Justin F. Shaffer
Department of Chemical and Biological Engineering
Colorado School of Mines


In 1983, Earl Washington "confessed" to a violent crime that he did not commit and was sentenced to death row. After spending seventeen years in prison for something he didn't do, Earl was released in 2001 after his innocence was proven through the use of modern DNA technology. This clicker case guides students through the wrongful incarceration of Earl and explores the biological mechanisms behind DNA profiling and using DNA evidence in criminal cases. Students will answer clicker questions about the criminal justice system, the polymerase chain reaction, agarose gel electrophoresis, and STR analysis, and ultimately will be able to use DNA profiling methods to match a suspect to a crime scene. Students also will be able to explain how learning biology is important even for non-technical careers. The case was developed for a lower-division introductory biology course for majors and non-majors students, but it could also be used in more advanced courses if time is dedicated to analyzing PCR, electrophoresis, and STR analysis.


  • Explain how PCR is used to amplify DNA molecules.
  • Predict the size of a DNA molecule using gel electrophoresis.
  • Explain how STRs are used in DNA profiling.
  • Use DNA profiling results to match a suspect to a crime scene.
  • Evaluate the use of DNA profiling methods in criminal investigations.


DNA profiling; PCR; electrophoresis; STR analysis; crime; crime scene; criminal investigation; forensic investigation; forensics; criminal justice; injustice; wrongful imprisonment; death row

Topical Areas

Ethics, Legal issues, Social justice issues

Educational Level

High school, Undergraduate lower division, Undergraduate upper division


PDF, PowerPoint

Type / Methods

Clicker, Directed, Interrupted



Subject Headings

Biology (General)  |   Biotechnology  |   Molecular Biology  |   Forensic Science  |  

Date Posted


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Bill Ferzoco
South Lakes High School
Reston, VA
I plan to use this as part of a PBL for my IB (International Baccalaureate) Biology class. I will let you know how it goes.

Nadia Sellami
Life Science Core Education
I used this case in my flipped intro to Molecular Biology class and it went really well - the students were really engaged! Thank you for putting this together!

Nancy Kochis
LaSalle-Peru high School
LaSalle, Illinois
I plan to use this in the DNA segment in my senior forensic science classes.