There comes a time in all parents' and caretakers' lives when they must ask - and attempt to answer - the critical and dreaded question: poop or chocolate?
Here is handy series of steps to follow when your child bounds into the room sporting a suspicious smear.
1.) If child is reliably verbal, ask whether substance is poop or chocolate. If credible witness (i.e. sibling, babysitter, grandparent) is nearby, attempt to corroborate this report. If child is not reliably verbal or you are in doubt of whether or not any available witness is credible, move on to step 2.
2.) Inspect the surroundings. Try not to act panicked or angry as this may alarm child or unreliable witness and they may attempt to hide evidence. Is there an open chocolate/granola/candy bar wrapper anywhere in the vicinity of child in question? If yes, this is strong evidence for chocolate. However to be safe (or if no) move on to step 3.
3.) Inspect the hands or feet or other body parts of child. Attempt to ascertain whether substance looks more like poop or chocolate. If this is inconclusive, move on to step 4.
4.) Sniff test. If you are brave (or female) you can attempt to smell the substance in question. (Note to the very brave: do not taste.) If you have a weak stomach (or are male) move on to step 5.
5.) Removal of soiled clothing followed by laundry (if clothing is affected) or bath (if skin/hair/ or other body part of subject is affected). Bath is advised in either case. Sometimes determining provenance of mystery substance is less important than simply taking care of business. Erring on the side of caution is always a reasonable plan under such circumstances. If you are unable to remove clothing and/or access laundry or bath, proceed to step 6.
6.) Presumably you have baby wipes, hand sanitizer, and/or bottled fluids (i.e. milk/water/juice) on hand. MacGyver that stain out with whatever tools necessary and available. You are a parent. You conceived it, you clean it. If unable to clean with available tools, create diversionary stain (using ink, cheese, tomato sauce, peanut butter, etc.) and attempt to gloss over suspicion of poop by saying loudly to subject "Let's not smear chocolate (or ink, cheese, etc.) on our pants again, okay?" If previously unforthcoming child suddenly becomes perversely verbal and volunteers the fact that said smear was in fact poop, laugh and tousle hair with a jovial "You are such a sillyhead!" and beat a hasty retreat.
Advice for similar circumstances:
Poop or peanut butter?
Follow above steps substituting "peanut butter" for "chocolate" and "peanut butter jar/granola bar/sandwich" for "chocolate/granola/candy bar wrapper" in step 2.
May also use "bear test" if bear is available, as bears love peanut butter and can be relied upon to lick at it. Occasional false positives will occur as bears will also sometimes lick at/maul non-peanut butter presentations. Not recommended if you are fond of child or if bear is rather hungry.
Poop or blood?
Follow above procedure, but in step 2 investigate child [as well as sibling and witness(es)] for injury. Especially critical if you have opted to employ the "bear test" for poop or peanut butter.