To establish a theft loss, a taxpayer must first prove the occurrence of a theft under the law of the relevant jurisdiction. See Monteleone v. Commissioner, 34 T.C. 688, 692 (1960) ("For tax purposes, whether a theft loss has been sustained depends upon the law of the jurisdiction wherein the particular loss occurred."); Giunta v. Commissioner, T.C. Memo. 2018-180, 116 T.C.M. (CCH) 446, 450; Enis v. Commissioner, T.C. Memo. 2017-222, 114 T.C.M. (CCH) 552, 557 ("[T]he taxpayer must prove * * * that a theft actually occurred under the law of the relevant State * * * [or] under an applicable Federal criminal statute."). The taxpayer must then establish the amount of the loss and the year in which the loss was sustained.