Nancy Guthrie Case: Sheriff Issues Warning About Major Issue

Pima County Sheriff Chris Nanos is spearheading the local investigation into Nancy Guthrie's disappearance, not without some controversy. Nanos said he has 400 personnel working the case, which is now in its 22nd day.

In a new interview this weekend, Nanos discussed some of the DNA evidence collected from Guthrie's Tucson, Arizona home, which may present some "challenges" as authorities enter it through nationwide databases.

'Mixed' DNA making things harder

In an episode with "NBC Nightly News" that aired Saturday...