Because there would definitely seem to be a killer on the road:

Long used to kidnappers and drug hitmen, Mexico's capital is now in fear of another type of criminal: a serial killer in women's clothes who strangles and batters old ladies in their homes.

Police believe a single murderer is responsible for the unusual killings of four elderly women in the city so far this year and may have committed some of 37 others since 2003.

True-crime fans (you know who you are) should have a great time with this one.