## Facts

- A bomb exploded at Thomas L. Shay Sr.’s home in Roslindale, Massachusetts, killing one Boston police officer and severely injuring another who had responded to a suspicious object in the driveway.
- The prosecution’s theory was that Alfred Trenkler built the Roslindale bomb for Thomas A. “Shay Jr.” to use against Shay Jr.’s father.
- Trenkler was charged in a superseding indictment with (1) conspiracy (18 U.S.C. § 371), (2) receipt of explosives with knowledge/intent they would be used to kill, injure, intimidate, or damage property (18 U.S.C. § 844(d)), and (3) malicious destruction of property by means of explosives (18 U.S.C. § 844(i)).
- Trenkler was severed from his codefendant and tried separately; a jury convicted him on all counts after a lengthy trial.
- To prove identity of the bomb maker, the government introduced evidence that Trenkler admitted building a similar bomb that exploded in Quincy, Massachusetts in 1986; the government argued the similarities in design and construction indicated a single maker.
- The government also presented ATF EXIS database testimony that, among thousands of reported incidents, only the Quincy and Roslindale devices shared the queried characteristics.
- Additional evidence included testimony that Trenkler made incriminating statements to another inmate and circumstantial evidence linking him to Shay Jr. and bomb construction.

## Issues

1. Whether admitting evidence of the 1986 Quincy bombing to prove identity violated Fed. R. Evid. 404(b) and should have been excluded under Fed. R. Evid. 403.
2. Whether testimony derived from the ATF EXIS bomb-incident database was inadmissible hearsay and, if so, whether its admission required reversal.
3. Whether admitting certain out-of-court statements by Shay Jr. violated hearsay rules or the Confrontation Clause.

## Decision

- The First Circuit affirmed Trenkler’s convictions.
- The court held the Quincy bombing evidence was admissible under Rule 404(b) for the non-propensity purpose of proving identity and survived Rule 403 balancing.
- The court concluded admission of the EXIS database evidence was erroneous under the hearsay rules (including as offered through a residual exception theory), but the error was harmless beyond a reasonable doubt given the remaining evidence.
- The court upheld admission of the challenged out-of-court statements as properly falling within hearsay exceptions (including state-of-mind use) and found no Confrontation Clause violation under then-governing doctrine.
- A partial dissent argued the EXIS evidence was highly influential “scientific-looking” proof built on unreliable reports and that its admission was not harmless.

## Legal Principles

- Other-acts evidence is admissible under Rule 404(b) only if it has “special relevance” to a material issue (such as identity) independent of propensity reasoning.
- Identity-based Rule 404(b) evidence may be admitted when the charged and uncharged acts share sufficiently distinctive similarities to support an inference of common authorship.
- Even when other-acts evidence is specially relevant, it must be excluded under Rule 403 if unfair prejudice substantially outweighs probative value; limiting instructions may reduce, but do not eliminate, prejudice concerns.
- Computerized or database-derived incident summaries offered for the truth of their contents can constitute hearsay; erroneous admission may be affirmed on harmless-error grounds when the verdict is strongly supported by independent evidence.
- Out-of-court statements may be admissible when offered for a recognized nonhearsay purpose or within a hearsay exception such as state of mind; Confrontation Clause analysis follows the governing constitutional framework applicable at the time of trial and appeal.

## Conclusion

The First Circuit upheld Trenkler’s bombing convictions, approving prior-act identity evidence under Rules 404(b) and 403, treating the admission of ATF database summaries as hearsay error but harmless on the full record, and sustaining limited use of a codefendant’s out-of-court statements under established exceptions without a Confrontation Clause violation.


United States v. Trenkler, 61 F.3d 45 (1st Cir. 1995)