Basar SheNitalem Min HaAyin
This is the approved revision of this page, as well as being the most recent.
- From the Torah law, any time a piece of meat is found and one is unsure whether it is kosher or not, one may rely on majority. If majority of the butchers in town sell kosher meat, then one may presume that it is kosher. However, the Rabbis forbid any piece of meat that wasn't kept in sight of a Jew except in certain cases. 
- If a piece of kosher meat left one's eyesight it is presumed to be non-kosher unless it has a unique identifying mark, one recognizes its look and one is certain that it is the same piece of meat, or it was wrapped and sealed. 
- The Ashkenazic minhag is that anytime one leaves a piece of meat and finds it in the same place that one left it, it is presumed to be kosher. 
- For Sephardim, if one left meat in one's house and one's windows are closed so that birds can't come in, or if the meat was covered and remained covered, it is kosher. 
- Shulchan Aruch YD 63:1
- Shulchan Aruch YD 63:1, Yalkut Yosef YD 63:2
- Rama YD 63:2 writes that the minhag is to assume that as long as the piece of meat is in the same place as it was earlier, it is the same piece of kosher meat. Be'er Heitiv YD 63:6 cites a dispute between the Shach who follows the Rama and the Taz who is even more lenient. Aruch HaShulchan YD 63:9 also rules like the Rama.
- Yalkut Yosef YD 63:1