Attorneys for disgraced South Carolina lawyer Alex Murdaugh are pointing the finger at Murdaugh's cousin Curtis "Eddie" Smith.

In a new court filing, the lawyers say that Smith, who reportedly failed a polygraph, should have been more rigorously investigated as a prime suspect by police.

During a polygraph five months ago, Smith was asked three times about his involvement in the shootings that killed Maggie and Paul Smith. Smith replied, no, to those questions, meaning he was not involved.

Police sources say Smith's answers indicate an attempt at deception. He lied. Smith has said he was “nowhere near” the property when the shootings occurred.

Joining Nancy Grace Today:

Jessica Garth - Chief, Special Victims & Family Violence Unit, State's Attorney's Office, Prince George's County, MD
Dr. Shari Schwartz - Forensic Psychologist (specializing in Capital Mitigation and Victim Advocacy), PantherMitigation.com, Twitter: @TrialDoc, Author: "Criminal Behavior" and "Where Law and Psychology Intersect: Issues in Legal Psychology"
Joe Scott Morgan - Professor of Forensics: Jacksonville State University, Author, "Blood Beneath My Feet", Host: "Body Bags with Joseph Scott Morgan"
Dr. Michelle DuPre - Former Forensic Pathologist, Medical Examiner and Detective: Lexington County Sheriff's Department, Author: "Homicide Investigation Field Guide" & "Investigating Child Abuse Field Guide", Forensic Consultant, DMichelleDupreMD.com
Chris Byers - Former Police Chief Johns Creek Georgia, 25 years as Police Officer, Private Investigator and Polygraph Examiner, www.chrisbyersinvestigationsandpolygraph.com
Anne Emerson - Senior Investigative Reporter, WCIV ABC News 4 (Charleston, SC), Host of Award-Winning Podcast: "Unsolved South Carolina: The Murdaugh Murders, Money and Mystery, Twitter: @AnneTEmerson

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Legal Heir Alex Murdaugh, Suspect in Wife & Son's Murders Names 'REAL KILLER'