"You don't want a couple of people who may not be reporting accurately to really skew the results, " said study co-author David Hemenway.

WSJ: Gun Counts Can Be Hit-or-Miss

That true story, reported in the Boston Globe in 1994, appears on page 70 of the classic study " Private Guns, Public Health" by David Hemenway, director of Harvard's Injury Control Research Center.

CNN: Obama needs a 'Plan B' on guns

Here's another case, as reported by Hemenway.

CNN: Obama needs a 'Plan B' on guns