the original claims ends in a circular sourcing:
The Training Institute on Strangulation Prevention says:
According to the Training Institute on Strangulation Prevention, “A
woman who has suffered a nonfatal strangulation incident with her
intimate partner is 750% more likely to be killed by the same
perpetrator…with a gun.
This article by Glass, Laughon, Campbell, Wolf, Block, Hanson, Sharps, Taliaferro
"Non-fatal strangulation was reported in 10% of abused controls,
45% of attempted homicides and 43% of homicides"
This seems to uphold the claim somewhat, showing a far higher risk for homicide in an abusive relationship that includes strangulation, though not at the 7.5-times factor the claim puts forward.
Weirdly, the same article says:
"Wilbur and colleagues' in 2001 found that 68% of a convenience
sample of 62 women presenting to a domestic violence advocacy program
reported strangulation by their abuser"
i.e compared to that, the ~50% previous strangulation they found in their murder sample would suggest previous strangulation is actually negatively correlated with later murder(&-attempts). Their own numbers came from finding women that reported abuse on randomized cold calls, though, and the 68% figure relates to a sample of women (self?)presenting to an advocacy program, so possibly already suffering from far higher levels of abuse.
"The Chicago Women’s Health Risk Study (CWHRS) found that 24.6% of
57 adult women killed by a male intimate partner in 1995 or 1996 in
Chicago were killed by strangulation or smothering" , and later,
ibid: "There was no difference between women who were not killed and
the women who were killed in having experienced prior choking or
so the actual predicitve quality of strangulation seems rather weak, overall.
But: The claim was murder by the same perp, and with a gun, which might wildly sway the statistics. Also, it is never explained against which baseline this would work? Strangulated women vs all women? Strangulated vs all IPV victims?
Strange addendum: there is a "twin" study from 2003 that mirrors Glass et al 2009 on the time frame of the murders, the number of cities, even down to the size of the random control base and their verbatim description
"A total of 4746 women met the age and relationship criteria and were read the consent statement." Glass et all 2009 and Campbell et all 2003
The 2003 study does not go into strangulation, though. honi soit...