Analysis of Competing Hypotheses

ACH was created and brought forth by Heuer (1999).[1] In the context of ACH, a hypothesis is viewed as a “potential explanation or conclusion,” which is tested by collecting evidence and arguments.[2] The method of ACH requires the explicit identification of all plausible alternative hypotheses and lays them in competition for favor by the practicing investigator while minimizing cognitive limitations.[3] This method is a break from the traditional approach of qualitative intuitive reasoning.

The primary strength of ACH is its diagnostic value. Traditionally, investigators formulated hypotheses and than intuitively selected the preferred hypothesis.[4] Essentially, investigators only collect and consider evidence that supports their preferred hypothesis, i.e., preferred suspect. In turn, the evidence brought forth to support the preferred hypothesis has no diagnostic value. Diagnostic value of evidence cannot be overlooked.

Diagnostic value can be framed as the specific evidence’s value across all hypotheses. Diagnostic value is not the support of all hypotheses, but the explicit support of one select hypothesis.[5] Heuer (1999) asserts that a common experience, through using ACH, is that analyst find favored evidence supporting their preferred hypothesis simultaneously supports several other hypotheses. In turn, the evidence holds no diagnostic value. Heuer (1999) makes a solid determination that diagnostic evidence should drive judgements. Thus, judgements through ACH become highly objective.

Criminal defense investigations are able to meet the following objectives through ACH.

1. Determine specific evidence not only supports the opposing criminal theory but several alternative theories
2. Identify critical evidence based on diagnostic value


The above description is written in the context of criminal defense investigations. The specific method is not limited to criminal defense, and can be applied to a wide array of problem sets.


1 Heuer, Richards J. Psychology of Intelligence Analysis. Center for the Study of Intelligence, 1999., p. 95
2 Ibid
3 Ibid
4 Ibid
5 Ibid, p. 102
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