There is a doctrine in criminal law that information derived from illegal searches by the police may not be admitted as evidence in a court of law. Even any information flowing from information from an illegal search may not be admitted as evidence in a court of law. This doctrine is called the the Fruit of the Poisonous Tree. This law prohibits the police from benefiting from something that started out illegally. This is how I see the Law of Karma working as well.
If the foundation of what we do is based in negative karma, then everything flowing from it is fruit of the poisonous tree. I have seen people do very hurtful and harmful things to others, and any benefits derived from this negative karma is doomed as well. For example, two people engage in infidelity with each other and lie to their spouses about it. They then end up in a relationship with each other. There will forever be doubt about whether they will cheat on one another. The lies they told to their spouses may be the very lies they tell each other in this later relationship.
In other words, their subsequent relationship is the fruit of the poisonous tree. The poisonous tree was the infidelity they perpetrated against their spouses, and anything flowing from it also is poisoned and doomed. I believe karma works in this way, because for every action there is an opposite and equal reaction, also known as Newton’s Third Law of Motion. What you do to others will return to you! Therefore, do good and good will return to you! (Copyright 2016 Awakening Journey with All Rights Reserved)