Everyone knows Sherlock Holmes, but most people have not heard of Edward Locard–often referred to as the Sherlock Holmes of France. Locard was a pioneer in the use of forensic science to solve crimes, particularly the science of trace evidence.  He posited that every contact leaves a trace. A criminal always leaves something behind at the scene of a crime s/he commits and takes something from that scene with him/her.  And what is left behind and what is taken can later be used as evidence against the perpetrator.  His theory (whose concept is now common knowledge to everyone who has ever watched a forensic science tv show) is called Rocard’s Exchange Principle.

Today’s modern, savvy criminal knows how to avoid leaving and picking up trace evidence–or at least they think they do. Latex gloves can’t guarantee that you won’t leave fingerprints.  And if you want to make sure you don’t take an evidence with you, you might be able to get away with dressing in a Tyvek head-to-toe jumpsuit and burning it after your endeavor (I’m not a criminal, but an avid reader of crime novels).  But no matter what lengths you go to, Rocard’s Exchange Principle applies. Something is taken and something is left behind.

We would do well to apply Rocard’s principle to all of our exchanges–acknowledging that for every contact we make with another person, we leave something behind and we take something with us.  We should not minimize the effect we have on other people when we make contact.  We can leave them with the kind of trace evidence that improves their day, their attitude or even their self-worth, or we can leave them with the kind of trace that hangs on and weighs them down.  What if we initiated every encounter thinking about what we leave behind? Being present to what the evidence of our presence in that person’s life will be.  From the cashier at the grocery store to our closest friends–every contact leaves a trace.

We should pay attention to the trace we take with us as well. Sometimes we need to recognize that what we have taken with us is not something we need to hold onto, and we should be intentional about ridding ourselves of it.  Just because a trace is left doesn’t mean it can’t be washed away, tossed out or left behind.

May we be present to the power of our presence. May we pay attention to what we do and don’t take with us from encounters with others, and may the trace evidence we leave behind be the stuff others want to hold on to.

Rev. Anne Russ is an ordained pastor in the Presbyterian Church (USA), currently based in New York City. Doubting Believer provides tools and encouragement for the rollercoaster ride of your faith journey. Follow me on Facebook , Instagram and YouTube. You can also follow on TikTok. Get emails to keep up with all that is happening.