I’m going to address the “lies and damn lies,” and get more into the damaging effects of what I see as undeniable elements of sexism permeating this case (and other cases) in a separate post, but this post is about the “statistics” portion. The statistics Ethan and I discussed in episode 15 were primarily derived from two sources. The first was a 2012 special report authored by the Bureau of Justice Statistics titled, “Violent Victimization Committed by Strangers, 1993-2010.” The second was a 2016 academic paper titled, “A Profile of Missing Persons: Some Key Findings for Police Officers,” by Prof. Shaunagh Foy.
The clip we played in the episode was from a recent episode of the Mary Buck podcast. It summarizes one of the more vocal perspectives on the “statistical likelihood” of various outcomes in the case. The crux of the argument is this:
Serial killers are rare, and most homicides are committed by a person known to the victim. Therefore if Maura is a victim of foul play, then the offender must be someone she knew.
To be fair, I agree that serial killers are rare and that most homicides are committed by a person that is known to the victim. That said, the problem with the reasoning above is that it ignores the thousands of stranger homicides that occur every year in the U.S. that are not committed by serial killers. It also overlooks the fact that crimes that are “random” in nature (such as stranger homicide) are the most difficult cases to investigate and most likely to remain unsolved.
Here is a recap of the numbers we mentioned in the episode (plus a few we didn’t mention).
Violent Victimization by Stranger
Between 1993 and 2008, about 21% - 27% of homicides were committed by strangers. Notably however, the relationship between the victim and the offender could only be determined in about 53% - 62% of cases. Thus according to the report, if the victim-offender relationship was known for all homicides, it is likely the rate of stranger homicides would actually increase.
In the episode, I used conservative estimates (15% of 15,000 annual homicides) to posit that about 6 stranger homicides occur each day in the U.S. If we use the BJS’s estimate of 21% - 27%, and the precise average annual homicide total between 1993 – 2008 (17,964), then the daily rate of stranger homicide rises to about 10 – 13 (again this is likely higher after factoring in homicides for which the relationship between the victim and the offender could not be determined).
Location: 50% - 58% of stranger homicides occur in public places, compared to about 17% - 21% of cases in which the victims knows the offender. By far the most common place(s) to be victimized by a stranger are “open areas, on the street, or on public transportation,” accounting for about 27% - 31% of all violent victimizations by strangers. (BJS - Table 6)
About half (47% - 49%) of violent victimizations by strangers occurred while the victims were away from home (travelling, shopping, or participating in leisure activities). (BJS - Table 8)
Circumstances: Between 26% - 29% of violent victimizations by strangers involved multiple offenders, whereas multiple offenders were involved in only 10% - 12% of incidents in which the victim knew their offender(s). (BJS - Table 11)
The circumstances surrounding stranger homicides seem to vary widely, but the most common circumstance (23% - 26%) is “other arguments.” The second most common circumstance (19% - 28%) involves robbery. (BJS - Table 13)
Outcomes of Missing Persons
Foul play was the most common outcome for those aged 18–25, accounting for about 39% of cases. Runaways were the most common outcome for those aged 17 and under, accounting for about 47% of the cases. And suicide was the most common outcome in the 41–65 age bracket, accounting for about 44% of the cases. (Foy - Fig 2.2)
Gender: The victim is a female in the majority of cases (71%) in which foul play is the cause of a person's disappearance. Only about 29% of disappearances resulting in foul play involve male victims. Outcomes involving suicide account for about 81% of cases involving missing men, and about 19% of cases involving missing women. (Foy - Fig 2.3)
Location: For missing persons in which the outcomes involved foul play, about 85% of the person reported missing was last seen in public. (Foy - Fig 2.4)
As Ethan alluded to in the episode, the unfortunate reality is that in many ways, Maura was the “perfect victim.” Simply stated, her “risk factors” (i.e. age, gender, and situational vulnerability) rendered her more vulnerable to foul play than any other demographic. When that is considered in light of what we know to be empirically true about the common circumstances surrounding stranger victimizations (i.e. traveling alone, being last seen in public, etc.), it is certainly possible (and perhaps even likely) that her disappearance is the result of being victimized by a stranger. And frankly, to suggest otherwise is either deeply disingenuous or extremely ignorant (or both).