It looks like access to Psychology Today is barred for people in Germany.

Must be copyright or licencing rules. Is an author credited? I might be able to look their work up somewhere else.
Big Lies and the Boogie Man
False abduction stories and murder
Published on April 26, 2013 by Joni E. Johnston, Psy.D. in The Human Equation
Summary of article:
Begins with a couple examples of mothers who falsely claimed their children were abducted when, in fact, they had murdered them.
Question: do lying murderers show tell-tale signs of deception when making a plea for their relative's return in front of camera?
Answer: most people are not able to spot a lie -- even seasoned police detectives.
2012 study in the Journal of Law and Behavior (Zwiebel -- maybe you can pull this one up -- this is the study referenced in the article)
http://psycnet.apa.org/psycinfo/2011-29347-001/
Cry me a river: Identifying the behavioral consequences of extremely high-stakes interpersonal deception.
ten Brinke, Leanne; Porter, Stephen
Law and Human Behavior, Vol 36(6), Dec 2012
In this study, researchers skilled in behavioral analysis viewed 78 videotapes of persons pleading for the return of a missing relative. About half of the videos were of guilty murderers, and half were innocent relatives, but the reviewers did not know which was which. Following certain cues regarding speech, body language, and emotional facial expressions, the behavioral analysts were able to correctly discern which relatives were murderers in 90% of the cases. "Failed attempts to simulate sadness and leakage of happiness revealed deceptive pleaders' covert emotions."
Selected quotes from Psychology Today blog:
"For example, throughout the entire publicized plea, genuinely distressed innocent relatives displayed sincere, full-face sadness and distress. In contrast, the faces of deceptive murderers were more likely to express mixed emotions (a surprised brow, a smirk, a sudden smile) in the face of an extremely grim subject. In particular, the facial expressions of murderers were more likely to contain the raised upper lip of disgust even when talking about the terror and sadness they were experiencing. (Although we don’t know the source of this disgust, the researchers hypothesized that disgust in this context was either an involuntary visceral reaction to the act of murder the deceptive pleader engaged in just days before, moral disgust or shame concerning one's actions, or a lingering revulsion for the victim).
In addition, the words deceptive pleaders used show the cognitive effort – and emotional strain – of living the lie. Deceptive pleaders, for instance, used fewer and more tentative, words throughout the plea, especially when directly appealing to the public for help. Deceptive murderers used tentative words to (unconsciously) avoid commitment in their words to distance themselves from or subtly communicate knowledge of a transgression. In this way, deceptive murderers subtly acknowledge that the victim will not be found alive, avoid commitment to the lie, and mitigate the psychological conflict resulting from the discrepancy between their secretly held and outwardly expressed knowledge."