An elderly couple was bilked out of $2,400 last week after a smooth talking con man led the Winston residents to believe their son was unwittingly caught with a large amount of marijuana while visiting Mexico, Winston police Officer Tim Swenson said Friday. The grifter posed as a police official who told the couple on Thursday their son had gone to Mexico City and had been involved in a traffic accident in which the friend was killed, Swenson said. They were told their son, who resides in Fort Worth, Texas, had hitchhiked to the hospital where his friend’s body had …