[henkster]

As a long time prosecutor, I discovered the five rules of successful criminal conduct:

1. Make it worth your while
2. Act alone
3. Do it only once
4. Never tell anyone what you are going to do or what you have done
5. Try to not be too obvious

Anyone who is caught and prosecuted has broken one or more of these rules. If the Boston Bomber kept these rules, it can be pretty tough.

[AppyPappy]

6. Don’t do it in a crowd. Too many witnesses.

If the guy put it down shortly before it went off, someone will remember that detail. The longer it sat there, the least likely someone will remember.
The biggest problem is that we have become less focused on “who and why” and more focused on “how”.

[Pollster1]

4. Never tell anyone what you are going to do or what you have done . . . If the Boston Bomber kept these rules, it can be pretty tough.

Fortunately, criminals and especially terrorists find this challenging. What is the point of murdering and maiming innocent people if you can't brag about it to your friends? I imagine the terrorist will talk.