And Now for Someone Completely Different: In Cat and Mouse Alex Cross gets knocked unconscious and taken to the hospital. The next chapter starts with, Thomas Pierce a brand new narrator, who was introduced earlier, while we're still reeling from the removal of Cross. He turns out to be, Mr. Smith, the second serial killer of the book, the same one he investigated.
Anonymous Killer Narrator: Almost every book contains this, except for the ones where the killer's identity is know from the beginning.
Artistic License - Law: Alex Cross's Trial is a prime example of this. In fact, it could be the poster child for this trope.
Batter Up: The Sojourner Truth School killer used a cut off, tape reinforced bat to kill his victims.
Blood Lust: Soneji in Cat and Mouse incorporates blood as a trademark.
Combat Pragmatist: Kiss the Girls has a woman who takes self-defense classes, with the Groin Attack recommended. When Casanova abducts her, she kicks him in the nuts. Unfortunately, Casanova was wearing protection. Because he had been watching her go to her self-defense classes.
The Casanova: The villain of Kiss the Girls is actually named Casanova, a criminal who builds a modern day harem of kidnapped women.
Dan Browned: Cross's encounters with role-playing gamers and vampires/goths. Might be a case of Did Not Do the Research.
Gory Discretion Shot: It's not uncommon for a chapter to end vaguely hinting at what has taken place. A particularly disturbing example from I, Alex Cross when the Big Bad, Zeus, visits the sex club that he frequents and takes two girls to his private room. After binding and gagging the two girls, he pulls out a taser gun and a pair of pliers before the chapter ends.
Idiosyncratic Episode Naming: At first children's rhymes, now with "cross" in the title. Still, if you can have a murder mystery titled Double Cross, you should.
The Last Dance: In Cat and Mouse, Gary Soneji, now dying of AIDS, goes on one last frenzied rampage, killing everyone he feels the need to and dead set on murdering Cross.
Madness Mantra: In Cat and Mouse, when Thomas Pierce is exposed as Mr. Smith, he starts repeating: I MURDERED ISABELLA CALAIS AND I CAN'T STOP THE KILLING. The first sentence is spelled out in his victims' initials. The second would have been.
The Mole: In Rose Are Red the Mastermind turns out to be FBI Agent Kyle Craig. He also helped out Casanova and the Gentleman Caller during Kiss The Girls.
Murder.com: The DC Audience Killer from Double Cross.
Our Vampires Are Different: The vampire cult in Violets Are Blue is more like the Manson Family than a group of vampires. Then again it's not exactly common for real vampires to appear in police fiction.
The Plan: Four Blind Mice is so strange that Neither Alex nor the contract killers figure out what the guy hiring them is doing.
Pun: In Cat and MouseMr. Smith "pierced" Isabella's heart.