The Fruit of the Poisonous Tree in IP Law

• Author: Mark A. Lemley
• Position: William H. Neukom Professor of Law, Stanford Law School; Partner, Durie Tangri LLP
• Pages: 245-269

245

The Fruit of the Poisonous Tree in IP Law*

Mark A. Lemley**

ABSTRACT: If a police officer searches my home illegally and finds evidence

of a crime there, the criminal law suppresses not only that evidence, but

evidence derived from the search that was not itself found illegally. This

doctrine is known as the “fruit of the poisonous tree.” The animating principle

of the fruit of the poisonous tree doctrine is but-for causation: If you had not

violated the law, you wouldn’t have found the evidence, and so you wouldn’t

have followed whatever investigative path was triggered by the finding of that

evidence. The newly discovered evidence—the fruit—is tainted by the poison

of the illegal search.

Intellectual property (“IP”) regimes face this issue when defendants infringe

an IP right in the course of making a product that does not itself infringe that

right. IP law is all over the map in dealing with such cases. Some IP regimes,

like trade secret law, apply the fruit of the poisonous tree logic, allowing the

plaintiff to recover not only for the profits the defendant made from secrets she

actually stole and used but also for the profits of any product that resulted

from the use of those secrets. Copyright law, by contrast, does not permit a

plaintiff either to obtain an injunction or to recover damages against non-

infringing final products. Patent law is somewhere i n between.

In this Essay, I offer a cohesive way to think about the fruit of the poisonous

tree in IP law. Whether IP remedies should extend to tainted but non-

infringing products should be a function of the mental state of the infringer,

the likelihood that infringement will be detected, and the contribution made

by the final, non-infringing product. Balancing those three factors won’t

necessarily lead all IP regimes to treat the fruit of the poisonous tree in the

same way. But it does both explain and suggest some needed reforms to the

current legal rules.

*

© 2017 Mark A. Lemley.

**

William H. Neukom Professor, Stanford Law School; partner, Durie Tangri LLP. Thanks

to Albert Alschuler, Jonathan Barnett, Dan Burk, Stacey Dogan, Rose Hagan, Tim Holbrook,

Herb Hovenkamp, Doug Laycock, Brian Love, Lisa Ouellette, Ted Sichelman, and participants

at a workshop at the University of San Diego for comments on an earlier draft.

246 IOWA LAW REVIEW [Vol. 103:245

I.INTRODUCTION ............................................................................. 246

II.WHEN DO NON-INFRINGING PRODUCTS INFRINGE? ...................... 249

A.THE LIMITS OF BUT-FOR CAUSATION ....................................... 249

B.INFRINGEMENT AND CAUSATION IN IP ...................................... 249

1.Trade Secrets ................................................................. 250

2.Patent Law ..................................................................... 253

i.Patent Law Generally Doesn’t Apply the Fruit of

the Poisonous Tree Doctrine ........................................ 253

ii.Circumstances in Which Patent Law Captures the

Fruit of the Poisonous Tree ......................................... 255

3.Design Patents ............................................................... 259

4.Copyright Law ............................................................... 260

5.Trademark Law ............................................................. 262

6.Punitive Damages .......................................................... 263

III. WHEN SHOULD IP OWNERS CAPTURE THE FRUIT OF THE

POISONOUS TREE? ........................................................................ 263

A.FACTORS TO CONSIDER ............................................................ 264

B.DO IP’S CURRENT RULES MAKE SENSE? .................................... 266

IV.CONCLUSION ................................................................................ 269

I. INTRODUCTION

If a police officer searches my home illegally and finds evidence of a

crime, courts refuse to admit not only that evidence, but evidence found

legally if it was ultimately derived from the search. This doctrine is known as

the “fruit of the poisonous tree.”1 The animating principle of the fruit of the

poisonous tree doctrine is causation: If you had not violated the law, you

wouldn’t have found the evidence, and you wouldn’t have followed whatever

investigative path that was triggered by finding that evidence. The newly

discovered evidence—the fruit—is tainted by the poison of the illegal search.

Civil law also concerns itself with chains of causation, both in

determining liability and in ordering relief. But it does not typically apply the

logic of the fruit of the poisonous tree to chase down every consequence of a

wrong. Tort law, for example, requires proof of both but-for and proximate

causation.2 In tort cases, plaintiffs can recover for some (but not all)

1. See Segura v. United States, 468 U.S. 796, 802 (1984); United States v. Ceccolin i, 435 U.S.

268, 275 (1978). Courts applying the fruit of the poisonous tree doc trine in criminal procedure

have struggled with some of the same questions of the extent of causation that I discuss in this paper.

See generally, e.g., Herring v. United States, 555 U.S. 135 (2009); Albert W. Alschuler, The Exclusionary

Rule and Causation: Hudson v. Michigan and Its Ancestors, 93 IOWA L. REV. 1741 (2008).

2. See Palsgraf v. Long Island R.R. Co., 162 N.E. 99, 102–03 (N.Y. 1928).