[s4e23] Roadkill -

is the 23rd episode of the fourth season of the crime procedural series Criminal Minds , which originally aired on May 6, 2009 .

The episode follows the Behavioral Analysis Unit (BAU) as they travel to , to investigate a series of vehicular homicides. The "Unsub" (unknown subject) uses a modified, heavy-duty truck as a weapon to run victims off the road or crush them. Key Plot Elements [S4E23] Roadkill

: David Rossi takes a lead role in empathizing with the suspect's physical limitations to help narrow down the profile. Notable Guest Stars Craig Sheffer : Portrays the Unsub, Mason Weaver. If you are looking for more specific details, The ending/climax of the episode. is the 23rd episode of the fourth season

: Penelope Garcia helps the team by tracking the specific modifications made to the Unsub’s vehicle, which was customized with hand controls to allow him to drive despite his paralysis. Character Highlights Key Plot Elements : David Rossi takes a