Last month with new details about the Aaron Hernandez murder case surfacing almost daily private detective Jay Groob sent Patriots owner Robert Kraft a sales letter. Groob pitched “investigative and security services” including “vetting due diligence and surveillance of personnel.”

As president of American Investigative Services and a licensed private detective in Massachusetts for 30 years Groob welcomed “the opportunity to consult with the Patriots and determine whether there is a particular need we can fulfill.”

Following Kraft’s first public comments about the Hernandez case the offer appeared well-targeted (though to date Kraft has not responded to Groob).

After authorities arrested Hernandez 23 on first-degree murder charges Kraft said he had been “duped” by the tight end. Speaking from his office at Gillette Stadium Kraft said he only knew “what goes on inside this building” and that “we don’t put private eyes on people.”

Groob and other local private investigators found those statements curious especially in reference to a player such as Hernandez who had arrived in Foxborough with questions about his past.

“To say Kraft only knows what’s going on in the building it’s like having blinders and earmuffs on” said private investigator Bob Long. “Is that all he wants to know?”

Long a former Massachusetts State Police detective and the first witness called in the James “Whitey” Bulger trial built a career on the close examination of criminals. Now he applies his law-enforcement experience to character due diligence and background checks. He counts professional sports franchises among his clients investigating potential team executives but not athletes.

“Due diligence is not anything new in sports” said Long president of Bob Long Investigations Group LLC. “It’s conducted on athletes because you’re investing millions and millions of dollars in them.

“A lot of teams are willing to take some risk. They keep their fingers crossed that nothing happens and have blinders on and earmuffs on and hope nothing blows up. Well in this case it did.”