Is the Instrument–Object Distinction in DNA Cases Coherent? Analyzing The Distinction in Commonwealth v. Ortiz
In recent Massachusetts DNA jurisprudence, courts have drawn a sharp distinction between objects treated as instruments of the crime and those characterized as mere movable property. That distinction played a decisive role in the Appeals Court’s decision in Commonwealth v. Luis A. Ortiz, where DNA found on a torn latex glove was deemed sufficient to identify the defendant as the perpetrator.
But does that distinction actually make rigorous analytical sense? Or does it risk collapsing careful sufficiency analysis into a post hoc narrative driven by outcome rather than principle?
This post examines whether the instrument–object dichotomy meaningfully constrains fact finding—or whether it merely repackages speculation as inference.
The Legal Problem DNA Evidence Creates
DNA evidence is uniquely powerful and uniquely limited.
It can identify whose genetic material is present, but it usually cannot determine when that material was deposited, how it got there, or whether the person was present during the crime. For that reason, Massachusetts courts have long required that when DNA on an object is the primary identification evidence, the Commonwealth must reasonably exclude the possibility that the DNA was deposited at a time other than the offense.
Historically, courts enforced this requirement by focusing on context: location, timing, durability of the object, and alternative innocent explanations.
More recently, however, courts—including in Ortiz—have leaned heavily on a conceptual move: reclassifying certain objects as instruments of the crime rather than as neutral, movable items.
The Instrument vs. Movable Property Distinction
In Ortiz, the Appeals Court emphasized that the latex glove was not simply an object found near the scene. It was treated as an instrumentality—something allegedly used to commit the offense itself.
That characterization did much of the work.
Once the glove was deemed an instrument of the crime, several analytical consequences followed almost automatically:
Its presence near the crime scene was treated as contemporaneous with the offense
DNA on the glove was inferred to have been deposited during the crime
Alternative explanations were discounted as unreasonable
By contrast, in cases involving masks, clothing, bandanas, or other portable items, courts have been more skeptical, emphasizing durability, secondary transfer, and prior handling.
The question is whether this distinction is principled—or merely convenient.
Why the Distinction Is Conceptually Fragile
At bottom, a latex glove is still a movable piece of personal property. It can be acquired, worn, discarded, reused, transferred, or planted—just like a mask, shirt, or tool.
Calling it an “instrument” does not alter its physical properties or resolve the central evidentiary problem: when was the DNA deposited?
The instrument label risks smuggling in the very inference the Commonwealth is required to prove. The reasoning can become circular:
The glove was an instrument of the crime
Because it was an instrument, it must have been used during the crime
Because it was used during the crime, the DNA must have been deposited then
But step one already assumes what step three purports to establish.
In that sense, the distinction may not add analytical rigor—it may simply reframe a narrative conclusion as a legal category.
The Real Work Is Still Context, Not Labels
Even in Ortiz, what actually carried the Commonwealth’s case was not the label “instrument,” but the surrounding circumstances:
The glove fragments were torn
They were found along an apparent escape path
They were discovered near recently stolen property
Similar glove fragments were found at the point of entry
Those facts—if credited—support a temporal and spatial nexus to the crime regardless of what the object is called.
Conversely, if those facts were absent, simply calling the glove an instrument would not cure the evidentiary gap.
That suggests the distinction is not doing independent analytical work. The court’s true inquiry remains the same: whether the totality of circumstances reasonably excludes innocent explanations.
The Risk of Outcome-Driven Reasoning
The danger of the instrument–object dichotomy is that it can become outcome-driven.
When courts are persuaded by the overall story, the object becomes an “instrument.” When they are not, it becomes “mere movable property.” The category follows the conclusion, rather than constraining it.
That flexibility may make decisions easier, but it weakens doctrinal clarity. Defendants and practitioners are left without a clear rule for predicting when DNA evidence will be deemed sufficient.
A Better Framework
Rather than relying on categorical labels, courts would be better served by explicitly analyzing:
The durability and reuse potential of the object
The likelihood of secondary transfer
The object’s proximity in time and space to the offense
Whether the object’s location is explainable absent guilt
Whether the Commonwealth’s inference depends on stacking assumptions
These factors already appear in the case law. They do not require an additional—and potentially misleading—instrument label.
Why This Matters
DNA cases are not just about science; they are about inference discipline.
When courts relax that discipline by relying on semantic distinctions instead of rigorous analysis, the risk of wrongful conviction increases—especially in cases where DNA evidence carries outsized persuasive weight.
Commonwealth v. Ortiz may have reached a defensible result. But the reasoning it employs raises an important question: are courts truly applying a principled sufficiency standard, or are they finding new ways to justify conclusions reached on instinct?
That question deserves continued scrutiny.
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