Nightly News | June 05, 2013
>>> of drones by the u.s. overseas. the president gave a speech on the topic. part of the appeal of using drones in place of live personnel is their accuracy but they may not be as precise as many u.s. officials claim. our report on this tonight from our chief foreign correspondent richard engel .
>> reporter: look at the tall man in white flanked by body guards. experts say it's osama bin laden in afghanistan one year before 9/11 in footage captured by the very first predator drone mission. but the drone isn't armed. a year later, drones are fitted with rockets and pakistan quickly turns into a hunting ground . an estimated 49 drone strikes under president bush . more than 300 under president obama .
>> conventional air power or missiles are far less precise than drones and are likely to cause more civilian casualties .
>> reporter: does the u.s. always know who drone strikes are actually killing? nbc news has examined classified documents detailing 114 drone strikes in pakistan in 2010 and '11. locations, death tolls, alleged terrorist affiliations. they also reveal what u.s. officials don't know like how many killed. between seven and ten in one strike, 20 to 22 in another. u.s. officials do seem certain they almost never kill civilians. in those 114 strikes, only one acknowledged civilian casualty .
>> they want to maintain the myth that civilians are not harmed with drone strikes which is implausible.
>> reporter: what's more, a quarter of those killed are described generically as, quote, other militants. it suggests u.s. oh officih -- officials don't always know how many or who they are killing. targets based on a signature profile. where they live, who they meet, who they talk to. several senior officials informed nbc news they had concerns about signature strikes. one told us the u.s. sometimes executes people based on circumstantial evidence. many counter terrorism officials insist drones are more precise than conventional attacks and they work. with a proven track record against al qaeda .
>> it's been a tremendous step forward in military technology . it's combined the capabilities of oh surveillance strike and long endurance in one platform.
>> reporter: drones are part of war now. but determining from afar who is a terrorist remains less precise than the weapons used to kill them. responding to our story a senior white house official told nbc news a major justification for many of the drone strikes is protecting u.s. troops in and around afghanistan . president obama has said as u.s. troop numbers in afghanistan goes down, so will the strikes.
>> richard engel with tonight's investigation. thanks for your work.