Or HaChaim on Genesis 44:10/אור החיים על בראשית מ״ד:י׳

1 ויאמר גם עתה בדבריכם כן הוא, He said: "also now I accept your words, etc." What does the word גם contribute to the legal aspects of what was taking place? Besides, what did the adjutant mean when he said: "it is as your words?" It appears that he did not accept their words; the brothers had decreed death on the thief whereas the adjutant had decreed only slavery!

2Perhaps the adjutant replied to the argument that they had proven their honesty by returning money they had found and were legally entitled to keep. The adjutant admitted that those who had previously returned to Canaan had indeed proven that they should not be accused of theft. Neither Shimon nor Benjamin had proven this, however.. Shimon had been in jail and Benjamin had not been in Egypt previously. The adjutant therefore reduced his suspicion from a collective one to one addressed to either Shimon or Benjamin. As to the death penalty, he was going to keep the thief as a slave until such time as it would please his master to execute him.

3Alternatively, the adjutant argued that the brothers were quite wrong legally. The death penalty is administered only to thieves who have been convicted by the testimony of witnesses who have observed the thief commit the crime. In this instance even the discovery of the stolen object would only be circumstantial evidence. The thief would therefore be guilty by reason of the local legal system, not by G'd's decree.

4ואתם תהיו נקיים, "whereas [the rest of you] will be innocent." You retain your presumption of innocence; the fact that the goblet will be found amongst one of you does not make you an accessory unless there was evidence that you were aware of the theft and had condoned it.