The Rambam writes [Gneiva 4-2]:
"וכן אם גנב חלבו ואכלו משלם לו דמי חלבו".
"So too if he stole forbidden fats and ate them, he must pay its value".
The Raavad is not pleased:
"וכן בחלבו משלם לו כפל דמי חלבו".
It is not just the value of the fats he must pay but double!
The Magid Mishna writes that the Rambam agrees with the Ravad but didn't find it necessary to write explicitly that there is a חיוב כפל.
The question is how do we find a חיוב of כפל? We know that כפל is a penalty [קנס] and קנסות are not given based on one's personal admission but rather based only on reliable witnesses. If so, it is עדות שאי אתה יכול להזימה - testimony where the witnesses can't be made into עדים זוממין [i.e. witnesses about whom two other witnesses say "you couldn't have been there because your were with us elsewhere" and then are given the same punishment that they intended to be given to the people about whom they testified]. Why? The עדים who testified that he ate חלב [fats] wanted to obligate him on two "charges" - מלקות for eating the fats and כפל for stealing and we say that they don't receive both lashes and pay - אין לוקין ומשלמין.
This is seen from Tosfos [כתובות לב: ד"ה שלא] who discuss a case where עדים testified about someone that he was מוציא שם רע [falsely accused her of infidelity] on his wife and thus tried to obligate her in both ממון and מלקות [and were found to be זוממין]. First Tosfos says that we can't obligate them in ממון and מלקות because אין לוקין ומשלמין - you can't get both. Then they turned around and said that it is not logical that they would not receive both punishments. In the Hagaos Taam Hamelech he explains that what Tosfos means is that there is a חידוש in the obligation of a מוציא שם רע that he is liable to two punishments - מלקות [as the pasuk says "ויסרו אותו"] and money [as the pasuk says that he has to pay מאה כסף]. Since they wanted to obligate him in a new type of חיוב for which the rule of קים ליה בדרבה מיניה doesn't apply, the חיוב that falls on them also doesn't have a דין of קלב"מ by virtue of the דין of כאשר זמם [they receive what they wanted to give]. So they will get BOTH! However when they came to obligate him money as a מזיק or גנב [and there is also a חיוב מלקות] where the din is that this חיוב ממון is absolved because of קלב"מ - the מלקות of the עדים also removes their חיוב ממון [see there].
According to that we can say as follows: When someone steals and eats חלב, his חיוב גניבה should be covered by the מלקות with no necessity to pay money [because of קלב"מ] and the only reason that he is liable to both punishments is because the חיוב גניבה preceded the חיוב אכילה [as the gemara says in Ksubos 32]. So with respect to the עדים זוממין who become liable to both punishments simultaneously because their false [and "zmama'ed] testimony obligates them in both מלקות and ממון, we can correctly state that they are not לוקין ומשלמין - they don't receive both מלקות and pay. Just like in principle קלב"מ applies to the accused person [and he only receives both punishments because of a technical issue - the גניבה preceded the eating], so too it applies to the עדים זוממין. It emerges then that this is עדות שאי אתה יכול להזימה [because we can't give them the double punishment that they wanted to give as a result of קלב"מ].
So the question is - How do we punish the person who stole and ate the חלב when the testimony about their acts is עדות שאי אתה יכול להזימה?
According to that we can say as follows: When someone steals and eats חלב, his חיוב גניבה should be covered by the מלקות with no necessity to pay money [because of קלב"מ] and the only reason that he is liable to both punishments is because the חיוב גניבה preceded the חיוב אכילה [as the gemara says in Ksubos 32]. So with respect to the עדים זוממין who become liable to both punishments simultaneously because their false [and "zmama'ed] testimony obligates them in both מלקות and ממון, we can correctly state that they are not לוקין ומשלמין - they don't receive both מלקות and pay. Just like in principle קלב"מ applies to the accused person [and he only receives both punishments because of a technical issue - the גניבה preceded the eating], so too it applies to the עדים זוממין. It emerges then that this is עדות שאי אתה יכול להזימה [because we can't give them the double punishment that they wanted to give as a result of קלב"מ].
So the question is - How do we punish the person who stole and ate the חלב when the testimony about their acts is עדות שאי אתה יכול להזימה?
