This question joins two systems that operate under different rules, so the honest answer separates them. In a court-martial sentencing hearing, sealed or otherwise sealed juvenile adjudications are treated very protectively, because the rules that govern what the government may prove in aggravation generally do not allow juvenile adjudications to be used as prior convictions. In a security clearance determination, by contrast, the underlying conduct behind a sealed juvenile record can still be considered, because clearance adjudication is an administrative national security judgment that reaches conduct rather than convictions. So the same sealed record can be largely off limits at sentencing yet still relevant to whether the member keeps access to classified information.
Why the two systems treat the record differently
Military sentencing is part of a criminal proceeding with strict evidentiary rules about what counts as a prior conviction. A security clearance determination is not a criminal proceeding at all. It is a forward-looking administrative assessment of whether granting or continuing access to classified information is consistent with the national interest. Because the questions are different, the treatment of a sealed juvenile record diverges. One system asks what may be proved against an accused as punishment, and the other asks whether a person can be trusted with secrets.
Treatment at court-martial sentencing
At sentencing under the Rules for Courts-Martial, the government may present limited categories of evidence, including personal data and the character of prior service drawn from personnel records, evidence of prior convictions, evidence in aggravation directly related to the offenses of which the accused was found guilty, and evidence of rehabilitative potential. The category that matters here is prior convictions. The governing rule defines a conviction narrowly, and juvenile adjudications are not treated as convictions for this purpose. As a result, a juvenile adjudication, sealed or not, generally cannot be introduced as a prior conviction in aggravation at a court-martial.
That narrow definition is deliberate. The same provision also excludes diversions without a finding of guilt, expunged convictions, minor traffic violations, foreign convictions, and convictions that have been reversed or vacated. Juvenile adjudications sit in that excluded group. The practical effect is that the protective treatment a sealed juvenile record receives at sentencing comes not primarily from the seal itself but from the rule that juvenile adjudications are not convictions the government may use against the accused.
There are limits to this protection. Sentencing evidence is also …