The difference between the two torts of conversion and trespass is fundamentally one of degree, trespass constituting a lesser interference with another's chattel, conversion a more serious exercise of dominion or control over it. Thus a trespass has been defined as an intentional use or intermeddling with the chattel in possession of another, such intermeddling occurring, inter alia, when the chattel is impaired as to its condition, quality, or value.
A "conversion," on the other hand, has been defined as an intentional exercise of dominion or control over a chattel which so seriously interferes with the right of another to control it that the actor may justly be required to pay the other the full value of the chattel. Whereas impairing the condition, quality or value of a chattel upon brief interference can constitute a trespass, intentional destruction or material alteration of a chattel will subject the actor to liability for conversion.
The scientist was accused of deliberately destroying cells developed by another scientist. The district entered judgment for the United States. The evidence was overwhelming in that the scientist admitted the tampering to three persons, the scientist had access to the laboratory at the time of the destruction, his fingerprints were found on flasks, and there was a motive in that the scientist had a rivalry with his fellow scientist. Conversion and trespass were similar torts, although conversion involved a more serious exercise of control. The intentional destruction of a chattel was an act of conversion. The intentional destruction of the cells, which were part of a valuable research project, was a conversion. The scientist acted with the necessary intent for an award of punitive damages.
Should the scientist be convicted of the crime of trespass and not conversion?
Assuming for the moment that a cell line is a chattel capable of being converted or trespassed upon, it is clear that the United States owned the Alpha 1-4 cell line, and that Dr. Arora's dominion or control it, while brief, was total. He intended to act inconsistently with Dr. Sei's right to control the cells, he did not act in good faith, and he committed the ultimate harm -- he destroyed the cells. While certain easily identifiable expense was caused by Dr. Arora's inappropriate acts, it is also apparent that he caused serious inconvenience to what was a critically important research project. By this analysis, if any tort was committed, it was unquestionably a conversion, not a mere trespass.