i also want to bring in eric fogle, maryland state police, retired. eric, you have worked with blood hounds, haven't you? >> yes, ma'am, i have. training for about 21 years and actually handled them myself. >> what can you tell us about the search that went on for david sweat? >> i can tell that you most likely use blood hounds. any time they found a point or article of clothing or article they would have touched, i'm sure they would have put a blood hound on that trail to make an attempt to find the direction of travel and kind of lead them to do an area that they could put all their resources in. >> how does that work exactly in the bloodhound picks up the scent of the person and then how long can he search for that scent? 's worth of work for this dog or what? >> yeah, i mean, they are able to trail for several days. the fresher the scent, the better. so if, let's say that he had touched something, an article of clothing or any type of object that you can confirm is him, they put the dog on that, at least determine the direction of travel. the human