Sweat Patches and Contamination

Many on pre-trial release or on probation are required to wear transdermal patches.  These patches measure various drug use by confirming the drug’s presence in sweat output taken through the skin.  Courts routinely hold that the results of these tests are presumptively correct.  See e.g., U.S. v. Meyer, 483 F.3d 865, 868 (8th Cir. 2007).

Despite this presumption of correctness, many exclaim that they did not consume any drugs.  Thankfully, the Courts have also recognized that no test is infallible. Id. at 869.  But, Courts have placed the burden of demonstrating compelling reasons of unreliability upon the defendant. Id.

The United States Department of Justice has sanctioned more than one study delving into potential unreliability and contamination of sweat patches.  Melissa Long and David A. Kidwell published a September 20, 2002 article finding that external drug contaminant on the skin can cause false positives. https://www.ncjrs.gov/pdffiles1/nij/196030.pdf.

They also term this false positive as passive exposure or contamination as the test subjects did not use the drugs.

Before examining passive exposure further, all courts require some form of chain of custody to be properly demonstrated before the results of a drug test are admissible.  In many cases, the patch comes with a chain of custody form.  The form should be examined to determine whether chain of custody has been legally established.  If not, this is a first line of defense.

One transdermal patch company posts its Training Manual and Technical  Questions & Answers on the Internet.  See, http://www.pharmchem.com/pharmchem/files/download_files/Patch_Training_Manual_Rev_Feb_2012_Final.pdf, http://www.pharmchem.com/pharmchem/files/download_files/Patch_Tech_QA_4-2012.pdf.  These are invaluable sources of information for proper application methods, which if not done correctly, could be potential sources of contamination:

The sweat patch can be contaminated either during the procedure
of applying the sweat patch or during the removal of the sweat patch.

In addition, if the individual applying the patch has drugs on their hands or gloves, and touches the absorption pad, those drugs may cause a positive test result. Similarly, if during the removal process of the sweat patch, if the individual that removes the absorption pad from the sweat patch has drugs on their hands, or on the disposable tweezers, and these drugs deposited in sufficient quantity onto the absorption pad, a positive test may result.


It does not appear that Courts have often overridden the presumption of reliability for the sweat patch.  However, one United States District Court has recently done so.  In U.S. v. McNutt, 2011 U.S. Dist. LEXIS 140714 (W.D.N.Y. December 11, 2011), the District Court, in finding that the positive sweat patch was due to environmental contamination, found the following evidence to be persuasive:

  • The Probationer’s husband smoked crack in their shared home;
  • The Probationer’s continued denial of drug use (when the accused used at previous times in the past she admitted it);
  • The almost contemporaneous urinalysis was negative; and
  • All of the Probationer’s subsequent drug tests since then have been negative.


In U.S. v. Snyder, 187 F.Supp.2d 52, 60 (N.D.N.Y. 2002), although the Probationer was revoked for other reasons, the Court also held that profuse sweating, which causes external moisture to the patch, could help outside drug contaminants penetrate the patches’ outer membrane – resulting in a positive result without actual use.   For example, Snyder describes how cocaine residue on U.S. currency can be transferred, if moist, to hands and then to the patch. Id.  Snyder describes how contaminated clothing could cause such a transfer too.  Id.

Also, McNutt indicates, and common sense would dictate, that if an alternate drug test is still a viable option, the Probationer should be sent for the alternate test.  For example, one could be sent for a hair test if within 90 days of the dates of alleged drug use.  A negative result on these other drug tests, while not 100% proof of non-use, is valuable evidence in supporting the position that the patch was contaminated.

Furthermore, when looking at much of McNutt, the case can be parsed into two dynamics: 1) was there opportunity for contamination; and 2) is the accused’s other conduct consistent with use or non-use.

On the whole, a case of contamination case be made to false positive results on a sweat patch.  One should check chain of custody; determine if there was opportunity for contamination; and marshal evidence consistent with non-use, including alternate drug testing, such as hair or urine.

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Michael Belancio

Michael Belancio has an array of litigation experience at the trial and appellate levels, representing both plaintiffs and defendants. His experience encompasses personal injury,... More about Michael Belancio

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