an anonymous letter sent to both the medical examiner and sheriff's office pointing fingers at adam yoder deadly poison could be found in his car. >> adam comes up to the sheriff's office. >> once he agreed to let us search his jeep. we go out with him to where his car is parked. >> they look underneath the seat and right where it said it was. in the letter. there is a package. >> along with colchicine was a crumpled receipt for the poison purchase. investigators called in caitlin, who had insight into the yoder family. they say she began pointing a finger at adam similar to the letter, prompting officers to ask if she had written it. >> so i again said, katie, if you wrote the letter, we need to know that. and it was at that point she admitted to writing the anonymous letter. we'd always said, you know, the person that wrote this letter is definitely you got to be considered a suspect in our case. >> caitlin would later denied to investigators writing the letter. >> did you write the letter? >> i can't talk about that. i'm sorry. >> can you say you did not write the letter? >> sorry. >>