When Paul is in the house talking with the kids, at 23:28 the fruit on the counter shows an orange and apple side by side. Seconds later at 23:30, two apples are suddenly side by side.
When Batista and Debra were discussing how serial killers were caught Batista said that Timothy McVeigh was caught because he was driving way too fast out of town, which was not the case. McVeigh's car was stopped on I-35 by Oklahoma Highway Patrol officer Charles Hanger because he was not displaying a license plate (he had a bill of sale which meant he was legal). When Officer Hanger approached the vehicle and made contact with McVeigh he noticed a bulge under his jacket and he acknowledged to the officer that he had a weapon. McVeigh was stopped because of the missing license plate, and was arrested because his conceal carry license was not valid in the state of Oklahoma.
Neil Perry's Florida driver's license is displayed: S914-614-40-943-0. The S signifies the first letter of the last name, which should be "P" for Perry. The two digit "40" is the year a person was born, which indicates this particular person was born in 1940, making him an unrealistic 81 years old.
When Dexter is talking about how embarrassed he is about thinking he was dealing with the master and "he lived in a double-wide". The trailer shown in the exterior shots is a single wide trailer that looks old enough to have been built before double wides existed; which was sometime in the late 1960s or early 1970s.
The phrase "double-wide" is used as a joke, however, just like "trailer trash".
In the scene where the dead high school yearbook editor is found, you can clearly see his neck pulse beating and his chest breathing.
The subplot involving the return of Rita's abusive husband, Paul, is not realistic. When he picked up the children from school without her consent, Dexter acted like there was nothing she could do when, in fact, her restraining order (mentioned previously) should have granted her custody and defined his visitation/parenting-time rights. Rita could have reported Paul for custodial interference, which is a crime. Contacting her likely also violated the terms of his probation, and she could have reported this to his probation officer.
Paul continues to break the conditions of his parole yet Rita still doesn't call the police.
Angel orders his forensics team to follow strict sterile protocol on the crime scene but none of them are wearing coveralls, face masks and such. They are all over the crime scene without so much as a hair net, only using thin latex gloves.
When, at 47:54, Dexter sees the headline "Teen Killer Arrested Again" (Jeremy Downs), the headline of the story below reads "Cultural Doner Gives All," misspelling "donor."