The term “signature” is simply another word for need, and when homicide investigators study a crime, they search for a motive, a reason for that crime. No one can determine with any accuracy or precision the factors or feelings which may motive and drive a man to murder, but the study of his crimes will reveal his signature. While some murderers may vary their methods of operation, choosing to stab, shoot or strangle their victims in an effort to deceive authorities or engage in experimentation, a killer’s choices, actions and words reflect his needs– even when he attempts to deceive and even when he does not realize that he is doing so. In this sense, the killer’s crimes will reveal his psychological fingerprint.
The Zodiac’s M.O., modus operandi, or method of operation, varied concerning the method of attack (including by knife and by gun), the choice of victims (couples and a lone male), the time of day for attack (early evening/late at night), and the location of attack (lovers lane areas, recreation area, residential neighborhood). These variations could be the result of experimentation, personal choice, some unknown plan, or an attempt to confuse investigators. The killer may have changed weapons, victims, and locations, but certain aspects of his crimes remain consistent and indicate his signature, his needs before, during, and after the attack. Each crime demonstrates a connection between his behavior and his needs, illustrating the process by which his behavior satisfies those needs. The killer’s reasons for killing may remain unknown but his behavior reveals his needs.
No list of Zodiac characteristics could be complete, but the 20 points listed below provide a portrait of the Zodiac by examining his actions.
Known characteristics of the Zodiac:
#1) The killer’s crimes often appear to lack obvious motive; meaning, no evidence of sexual assault, robbery of significant monetary value, or personal animosity.
#2) The killer makes little to no effort to conceal his actions, often choosing populated or popular areas as the locations of his attacks.
#3) The killer takes risks beyond those preferable to someone who has serious fear of capture.
#4) The killer’s crimes appear to be premeditated in nature, and often indicate preparation and planning.
#5) The killer can vary his methods but remains largely consistent in linking himself to these crimes rather than attempting to avoid detection of any connection.
#6) The killer enjoys recounting his deeds, either by telephone or written communication, including a message at a crime scene or handwritten letters.
#7) The killer often provides minor and/or important details: in some cases, the authorities state that these messages contain information known only by the killer.
#8) The killer favors victims of chance rather than preselected targets: couples on a roadside, a couple at a lake on a whim, or a cab driver passing by. The evidence suggests that he selected his targets at random.
#9) The killer can adapt to changing conditions and accomplish his goals, remaining calm under pressure and improvising when necessary. He has the ability to interact with his victims without raising suspicion.
#10) The killer can employ a carefully constructed ruse when it suits his needs. At Lake Berryessa, the killer concocted a curiously-false yet detailed story regarding a prison escape, the killing of a guard, and a flight to Mexico. He lied to his victims and claimed he only intended to rob them before stealing their car but the deception ended with a sudden ambush of violence. The selection of a cab driver and the direction to a pre-determined location also suggests planning as well as the ability to interact with and deceive a victim until the desired time to strike.
#11) The killer does not feel a need to interact with the victim after the initial violence other than to retrieve items he can later use for some known and/or known purpose, such as trophies or a possession which he can later use to prove that he was responsible for the crime. He does not sexually molest his victims, nor does he make any effort to transport them away from the scene of the crime. The killer makes no effort to conceal his crimes in that he does not dispose of or attempt to hide the bodies but prefers to leave the victims where they fall.
#12) The killer inflicts potentially lethal and often deadly wounds but makes no apparent effort to ensure that his victims are dead before leaving the scene of the crime. In two instances, rather than leaving his victims to die at isolated locations, the killer called authorities and directed them to the scene and the victims, thereby increasing the possibility that they might somehow survive.
#13) The killer’s crimes revolve around and concern vehicles: he drives to the locations where he attacks victims who are seated in vehicles, he asks for and/or takes the keys to the vehicles of his victims, he writes a message on the vehicle belonging to a victim, and he sits inside the victim’s vehicle in order to commit the crime. He even mentions and/or describes the vehicles of his victims in both his telephone and written communications.
#14) The killer repeatedly defines his crimes in reference to the method, the location and/or date of those crime. The killer refers to the victims he killed “last Christmass,” victims “one mile east of Columbus Parkway,” those people “up north,” and the taxi driver over by Washington and Maple streets. He even writes the location of his attacks on a car door as, “Vallejo,” as well as the dates of those crimes along with others. In his letters, the killer refers to the method of attack as shootings. He mentions the caliber of weapons and the brand and caliber of the ammunition used in the first two shootings. In his telephone calls to police, the killer states the caliber of the weapon used in the shooting at Blue Rock Springs Park. The message left on the door of the victim’s car at Lake Berryessa refers to the method of attack as “by knife.”
#15) The killer often describes his fantasies using vivid details.
#16) The killer enjoys describing the reactions of his victims but makes no significant effort to inflict pain on his victims beyond that which is necessary to the completion of his apparent goal to wound or kill: he does not engage in any acts of obvious or pro-longed torture and or sadism.
#17) The killer alludes to past and future victims, often without providing specific details or information.
#18) The killer often warns of further attacks or threatens more violence unless his demands are met. He will provide elaborate details regarding his potential reprisals.
#19) The killer often states that he will strike again yet many of these threats appear to be nothing more than attempts to frighten the public and/or mislead or confuse authorities.
#20) The killer links himself to and/or claims credit only for crimes which remain unsolved.