Some of that CSI comment might be true, but I don't have cable or satellite or even watch much TV (I'll catch programs at gym but that is about it, mostly news). I'll take it as a compliment I guess? I like to read as much as I can about crimes and forensics. History tends to repeat itself.
But the information listed above is factual. I would like to think that I might as well post a logical and constructive thought process about the topic, since my mind is always going.
The police stated that the FBI offered assistance and they immediately accepted. The FBI commonly offers assistance. Many times this is given in the form of use of the FBI Laboratory. The FBI only has the authority to intervene in an investigation when it meets the criteria you listed above.
The FBI was on scene the morning of the murder to assist in collecting evidence and also walked the Straubs around the house when they returned from their cruise.
They may be thinking "one less on the streets" but you can't carry that argument over to discuss the girlfriend, a full time nursing student and full time server.
I think some people overlook the importance of minute details in a case. People can polish an alibi, and lie all they want. Something as small and insignificant as a piece of duct tape, brand of zip tie, or, yes, even a unique plastic bag can link someone to a crime and focus the investigation on them.
I was just trying to supply a unique viewpoint about the situation in my previous post.