A letter from Jack the Ripper

 On 27 September 1888, Central News Agency in London received a letter signed 'Jack the Ripper'. It was probably a hoax. It's unlikely it was from the murderer but it gave him his name. It's almost certain now that we will never know the killer's real name, too much time has passed and things like the victim's clothes that might contain evidence were destroyed long ago because at that time they didn't see any point in keeping it. Obviously, they had no concept of DNA or other modern forensic techniques.

The first murderer caught by DNA evidence

 On 19 September 1987 Colin Pitchfork was arrested at his home in Leicestershire, England. He was the first murderer to be caught by DNA evidence. He was sentenced to life imprisonment in January 1988.

Beheaded in Denmark

  In Denmark beheading with an axe was the traditional method of execution. The last person in Denmark to be beheaded with an axe was Jens Nielsen in 1892. The guillotine was never used in Denmark but it was used just once in Sweden, in 1910.

True Crime Trivia

 I wrote another article. It's called True Crime Trivia.

Fingerprints

 On 13 September 1902 a burglar named Harry Jackson became the first person in Britain to be convicted by fingerprint evidence. He left a his prints on a freshly painted windowsill. Jackson was sentenced to 7 years in prison.

DNA

 On 10 September 1984 Alec Jeffreys discovered DNA fingerprinting. It has proved to be a vital tool for law enforcement. Colin Pitchfork was the first murderer caught by the new technology.

The last person guillotined

 On 10 September 1977, Hamida Djandoubi became the last person in France to be guillotined. The French abolished capital punishment in 1981.