The term "overdetermination" (German: Überdeterminierung) was used by Sigmund Freud as a key concept in his psychoanalysis, and later by Louis Althusser.
Freud wrote in The Interpretation of Dreams that many features of dreams were usually "overdetermined," in that they were caused by multiple factors in the life of the dreamer, from the "residue of the day" (superficial memories of recent life) to deeply repressed traumas and unconscious wishes, these being "potent thoughts".
Freud favored interpretations which accounted for such features not only once, but many times, in the context of various levels and complexes of the dreamer's psyche.
"In contemporary analytic philosophy an event or state of affairs is said to be overdetermined if it has two or more distinct, sufficient causes.
In this case, similar to the example of firing squads, Billy and Suzy together shatter the window and the result is not overdetermined.
Unless a circumstance-clause is included, the putative cause to which one wishes to draw attention could never be considered sufficient, and hence not comply with the counterfactual analysis.