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MO, Signature, & the Law

Offender Modus Operandi, Signature, and the Law - Codes and cases

Expert Testimony - Transcript of an 1108 Hearing

Definitions - Refining the language

Offender Modus Operandi, Signature, and the Law
by Brent E. Turvey, MS

In California, some interesting legislation and rulings have lead to the more frequent courtroom use of behavioral evidence relating to offender Modus Operandi and Offender Signature. Specifically, in death penalty cases involving the potential of multiple offenses committed on separate occasions (AKA serial offenses, most often involving kidnapping, arson, rape and homicide), the issue of linking cases by examining offender behavior has become very important. Below are three issues that this examiner has encountered in court or in casework.

Under California Penal Code section
1101(b) of the Evidence Code evidence of both charged and uncharged misconduct (cases where an offender is suspected, but not charges have been filed) may be admitted for the purpose of demonstrating a common plan, scheme, or design if the offenses are sufficiently similar (People v. Ewoldt (1994) 7 Cal.4th 380).

People v. Ewoldt (1994) 7 Cal.4th 380 does state that evidence of prior uncharged sexual acts is admissible at a subsequent trial for sexual offenses, in order to show a common design or plan on the part of the defendant. However, the court also found that "evidence of uncharged misconduct" may only be admissible if it is "sufficiently similar" to the charged offense "to support the inference that they are manifestations of a common design or plan."

No concrete definition of "sufficiently similar" is in use, meaning that there is no definite standard by which the courts are suggesting similarities must be evidenced.

Under California Penal Code section
790 of the Evidence Code, multiple offenses committed by the same offender in multiple counties may be consolidated for trial in a single county (thus introducing a highly prejudicial element) if it can be shown that the crimes are properly joinable, and that they are connected together in their commission.

No reasonable definition of "properly joinable" or "connected together in their commission" is in use, meaning that there is no definite standard by which the courts are suggesting similarities must be evidenced. It can be interpreted to mean connected physical evidence, in which case criminal profilers are not really necessary. But it can also be interpreted to mean connected together by behavioral evidence, in which case criminal profilers may find themselves being asked to consult on such issue.

California Penal Code section
1108 was recently added to the Evidence Code to provide a specific exception to 1101 in sex crimes cases where a person is charged with a sexual offense and the prosecution wants to offer evidence of prior or other sexual offenses to show a propensity to commit this offense, or the charged offense. This is a special exception to single out "sexual predators". The problem with allowing this type of behavioral evidence without physical evidence to back it up, according to Ewoldt, is that it is so prejudicial that its admission requires extremely careful analysis.

According to Ewoldt and Balcom, "The greatest degree of similarity is required for evidence of uncharged misconduct to be relevant to prove identity." People v. Ewoldt, 867 P.2d 757 (Cal. 1994); People v. Balcom, 867 P.2d 777 (Cal. 1994). Furthermore, "For identity to be established, the uncharged misconduct and the charged offense must share common features that are sufficiently distinctive so as to support the inference that the same person committed both acts. 'The pattern and the characteristics of the crimes must be so unusual and distinctive as to be like a signature.' (McCormick on Evidence, 4ht Ed., 1992)" (People v. Ewoldt (1994) 7 Cal.4th 380).

This is perhaps the most frightening legislation as it allows for the use of offender MO and signature behavior to infer guilt in a court of law. This was never the intended use of these investigative terms.

What all of this means for criminal profilers is very pointed:

1) The need to establish clear and consistently applied terms and definitions of offender Modus Operandi and Signature.

2) The need to recognize the difference between an investigative linkage, which serves during the investigative phase of a case, and a probative linkage, which is "sufficiently distinctive" as to be more probative than prejudicial. This in accordance with the dual role of a criminal profiler as an investigator alongside law enforcement, and a potential expert witness in area of criminal profiling and crime analysis in court.

State of California v. Johnny Duane Miles
Case No. FSB 09438

Evidence Code 1108 Hearing
January 6th, 1999

Expert Testimony of: Brent E. Turvey, MS

In this case, the examiner was asked to review the offender behavior in four cases. Briefly--

The question before the examiner was not whether or not the same person committed all four offenses, but whether the offender behavior in the four case (or any of them), by itself, evidenced a pattern that was sufficiently distinctive as to be probative to suggest linkage on that basis alone.

The answer given by this examiner was that it was not. Evidence of distinctive behavior simply was not consistent across the offenses, and the examiner could not interpret what was not present.

These definitions are taken in part from "Criminal Profiling: An Introduction to Behavioral Evidence Analysis" London: Academic Press, 1999. The terms investigative linkage and probative linkage were also developed by Brent E. Turvey, MS to address these issues as they have arisen in his casework. Please cite appropriately.

Modus Operandi: Modus operandi (MO) is a Latin term that means, "a method of operating." It refers to the behaviors that are committed by an offender for the purpose of successfully completing an offense. An offender’s modus operandi reflects how an offender committed their crimes. It is separate from the offender’s motives, or signature aspects.

Offender Signature (comprised of two parts):

Signature Behaviors: Signature behaviors are those acts committed by an offender that are not necessary to complete the offense. Their convergence can be used to suggest an offender’s psychological or emotional needs (signature aspect). They are best understood as a reflection of the underlying personality, lifestyle, and developmental experiences of an offender.

Signature Aspects: The emotional or psychological themes or needs that an offender satisfies when they commit offense behaviors.

Case Linkage: The general process of demonstrating discrete connections between two or more previously unrelated cases.

Investigative Link: A connection between one or more solved or unsolved cases that serves to inform the allocation of resources towards the investigation of fact.(i.e.- in terms of behavior, general or opportunistic circumstances of the offense; general similarities in modus operandi; and similar signature aspects evidenced by signature behaviors that are very dissimilar)

Probative Link: A connection between one or more solved or unsolved cases that is sufficiently distinctive as to support the inference that the same person is responsible(i.e.- in terms of behavior, distinctive, specific Modus Operandi and signature behaviors and signature aspects across multiple cases argued to evidence a probative link).

Updated 2/01/99
1998 Knowledge Solutions LLC