A cigarette contains up to a gram of tobacco with a nicotine content of 0.5 to 2 percent. A recent estimate of nicotine's human LD50 is in the range of 0.5 to 1 grams. A four cigarette dose would seem unlikely to be lethal.

http://www.inchem.org/documents/pims/chemical/nicotine.htm#P...

  7.2.1 Human data
    7.2.1.1 Adults
      The mean lethal dose has been estimated to be 30 to 60 mg (0.5-1.0 mg/kg) (Gosselin, 1988).
    7.2.1.2 Children
      The lethal dose is considered to be about 10 mg of nicotine (Arena, 1974).
  7.2.2 Relevant animal data
    Dog:     oral LD50:   9.2 mg/kg 
    mouse:   oral LD50:   3.3 mg/kg  (RTECS, 1985-86)
    rat:     oral LD50:   50 mg/kg

0.5-1.0 mg/kg, not 0.5-1.0 grams. Don't go eating cigarettes.

edit: http://abcnews.go.com/US/paul-curry-convicted-1994-nicotine-...

edit2: I see what you saw - http://link.springer.com/article/10.1007%2Fs00204-013-1127-0...

That's nowhere near true...