The standard of proof in internal investigations: which to use and how to declare it

Few questions reveal as much about the quality of an investigation as this one: under what standard of proof did it conclude? When the answer is silence or "based on the evidence," the file has a problem at its origin. The yardstick is not a technicality: it is what allows a third party to verify whether the conclusion was reasonable.

The three standards and what they demand

• Preponderance of the evidence. The conduct is more likely than not to have occurred. It is the standard of most workplace investigations and the one labor courts apply when weighing the ground for termination.
• Clear and convincing evidence. A high degree of certainty, short of absolute certainty. Reserved for conduct whose consequences are especially serious for the respondent, such as allegations bordering on the criminal.
• Beyond reasonable doubt. The criminal standard. It does not belong in an internal investigation, and demanding it amounts to never being able to conclude.

The most frequent error is not choosing badly but not choosing at all: investigating without a standard and deciding afterwards with whichever suits the outcome.

Why it is declared before starting

Declaring the standard in the investigation plan forces the evidence collection to be designed for that level of certainty. If the standard is preponderance, two consistent testimonies and a documentary record may suffice; if it is clear and convincing, additional corroboration will be needed. Deciding at the end invites adjusting the yardstick to the desired result, and that is exactly the accusation a litigator will try to prove.

How it is written in the report

One sentence suffices, as long as it appears: "The conclusions of this report are issued under the preponderance-of-the-evidence standard, in accordance with the investigation plan approved on [date]." Then, for each finding, the determination is expressed in the same terms: substantiated, unsubstantiated, or partially substantiated under that standard.

When the conduct is only partly substantiated, the report says so precisely. A file that acknowledges what it could not prove is more credible than one that proves everything.

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