1. Toulmin: Pulling out the Warrants
from Patricia Cornwell’s Portrait of a Killer: Jack the Ripper -- Case Closed

2. Cornwell’s central claim is that Jack the Ripper was really Walter Richard Sickert, a relatively well-known English painter of the late 19th Century.  

3. Conclusion: Sickert was Jack the Ripper.
DATUM: One of the letters that purported to be from Jack the Ripper was written on the same, relatively rare, brand of stationery as a letter from Sickert.
WARRANT?

4. Conclusion: Sickert was Jack the Ripper.
DATA: Sickert had an operation as a child that left him unable to have a normal sex life.  We know today that many serial killers are impotent.
WARRANT?

5. Conclusion: Sickert was Jack the Ripper.
DATA: Sickert painted a picture in 1908 called "Jack the Ripper’s Bedroom," described by an art historian as being "very dark and disturbing."  Sickert often painted scenes of violence against women. 
AND?