Mark Environment News Today

Have tamerlan tsarnaev on one government watch list well before the boston bombings. rick nelson is an expert on government databases. why didnt the watch list prevent this? >> difficult for the watch list in and of itself to stop the attack, it is just data, it is information. >> reporter: there are many watch lists, from border patrol to the fbi to the cia. the older brother and his mother were on one called the terrorist identities data mark environment or tide a low level list. something tha...