Editor's note: Frank Farley is a psychologist and L.H. Carnell Professor at Temple University, Philadelphia, and a former president of the American Psychological Association.
(CNN) -- The trial is over. Casey Anthony is not guilty, and I believe we will learn that the jury saw through the most unreasonable and bizarre piece of the prosecution's case -- the motive. Jurors followed the prosecution's instruction to "just use common sense," and found that the motive made none.
Without concrete evidence, the essence of this trial was psychology: How do emotion, love and mothering play a role; who is lying and how can we know that.
But the theories put forth were based on bad psychology. The prosecution said the motive was simple and two-pronged: Casey made a murderous decision because she wanted party time; and Caylee was getting to an age when she might be able to tell people about her mother's lies and activities. So Casey made a pre-emptive strike. These explanations were vigorously advocated by the prosecutors in their closing arguments and rebuttal as central to the jury's deliberations.
Arguments from prosecution and defense
No credible motivational psychology that I know of would support that a single mother who seemed to love her child and who had lots of back-up parenting, in the grandparents and perhaps even from a brother, would go through the careful planning and complex, unpredictable, scary process of killing and disposing of her child in order to get a bit more free time.
This could not be true, unless she was seriously mentally ill, and no available evidence showed that. To go against that deep human instinct to take care of a child, and instead kill that child, demands a very significant reward in the opposite direction, and partying doesn't rise to that level.
What sane human being could wake up in the morning and say, "Gee, I could have a fun time if I killed my daughter." There was also no evidence that Caylee was a difficult child whose behavior could lead her mother into a homicidal rage. This whole scheme goes against our deepest instincts rooted in thousands of years of evolution.
One of the closing images of the trial, shown at the end of the prosecution's rebuttal, was Casey Anthony's tattoo, "Bella Vita," or beautiful life. The tattoo was supposed to drive home the hedonistic urges that drove Anthony to kill her child. But just about everyone of her age today has, or wants, to get a tattoo. And tens of millions of young Americans Casey's age are setting out with the dream of a "beautiful life."
Infanticide versus no partying: No serious psychology supported this option during the trial.
Then there is the prosecution's second alleged motive for murder. At 2½ years, Caylee was getting to the age where she could reveal her mother's lies. But her parents, and anyone close to her, was probably aware of her propensity in this area. And Casey could have schooled Caylee in her own well-practiced habit of lying if she wanted to -- many kids lie for their mothers.
The prosecution said these motivations were crucial to deciding this case. The attorneys might have believed these ideas could sway the jury, pundits and the public, but in the science of psychology, they would not survive a student seminar. They are speculative and insufficient for any serious life or death deliberations.
Jurors decline to speak to media
The role of lies and lying permeated this trial. Lying, of course, is one of the behaviors courts are supposed to help sort out. Most people are incapable of detecting lying through facial expressions and body language. We often have a glib response, "It's obvious he's lying." And of course juries are often trying to catch lies -- but like the rest of us, they are bad at it.
There is a developing psychological science of detecting lies, and if it ever achieves a high level of accuracy and usability I would argue it should be allowed into legal proceedings. It is desperately needed.
I am not opining here on whether Casey Anthony was guilty, but raising serious questions about the distorted psychology implicit in major features of this trial. Clearly, the case raised profound questions of human behavior and the use of scientific psychology. No scientific psychologist was asked to testify. To my knowledge, no scientific psychology was anywhere referenced. That's a crime.
The opinions expressed in this commentary are solely those of Frank Farley.