<P> Days after the discovery of the bodies, Joseph McStay's father said the San Diego Sheriffs Department investigation was faulty . He filed formal complaints in 2013 . </P> <P> The circumstances surrounding the family's disappearance and the lack of clues about their whereabouts triggered speculation by amateur sleuths . Radio host Rick Baker published a book, No Goodbyes: The Mysterious Disappearance of the McStay Family . Baker began following the case in 2011, after interviewing Joseph's brother, Michael, on his program . Baker conducted dozens of interviews on the case (traveling to Belize, Mexico, Haiti and the Dominican Republic), followed leads and reported sightings of the family . Baker, critical of Summer McStay in his book, speculated that she might have committed the murders . Michael McStay criticized Baker and the book's accuracy, saying, "I don't know how he sleeps at night . I suspect he's looking for money . He's a good manipulator and knows how to twist things . He's just trying to sell books ." </P> <P> When the bodies were found, Baker offered a refund to those who purchased his book before November, 2013 . He said he did not believe that drug cartels were responsible for the deaths, citing the placement of the McStays' vehicle after their disappearance: "Why would they stage their car at the border, cartels don't do that ." Although involvement by the McStays with Mexican drug cartels was one of many theories suggested after their disappearance, no supporting evidence has been found . </P> <P> After their disappearance, it was speculated that the McStays left voluntarily, since investigators found searches on the family's computers for "What documents do children need for traveling to Mexico?" and Spanish language lessons . Because their car was found so close to the Mexican border, police reviewed surveillance footage of the pedestrian gate into Mexico . Video recorded the evening of February 8, released on March 5, showed a family of four resembling the McStays crossing the border into Mexico . On February 19, 2010, California police notified Interpol to be on the lookout for the family . In April 2013, the San Diego County Sheriff's Department announced that it believed that the McStays traveled to Mexico voluntarily . Several unconfirmed sightings of the family were reported in Mexico and elsewhere, perpetuating hopes that they were safe and had left voluntarily . Relatives of the McStays doubted that they would travel to Mexico, saying that Joseph and Summer avoided the country because of the safety threat posed by recent drug wars . Other critics of the theory noted that the McStays had more than $100,000 in bank accounts, with no withdrawal of funds in preparation for a trip, and their accounts were untouched after their disappearance . Summer's sister said Summer's passport was expired . Although it is possible for a U.S. citizen to enter Mexico without a passport, one is required to reenter the United States . </P>

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