Police Cars

I did not see the police cars in the movie in particular. I did look the movie up in the Internet Car Movie DataBase and they list only two sedans: a 1927 Cadillac series 314-A and a 1929 Lincoln Model L. Since the Lincoln is a convertible it is much more likely that the police cars were Cadillacs.

It may sound extravagant, but it was much more common for big city police departments to use Cadillacs, Buicks, Lincolns, Packards, or other luxury cars in the 1920s because they were roomy, fast, and reliable. Smaller towns and counties often could not afford such expensive machinery and were forced to use Dodges or Fords. I think this is why Clyde Barrow like the Ford V-8. It was cheap enough in the 1930's to be available to steal and the V-8 engine had enough horsepower for him to outrun local cops.

The best diplomat I know is a fully charged phaser bank.