Can you be arrested for shoplifting before attempting to leave the store with the item?

Yes, you can be arrested or detained for shoplifting before leaving the store. While in the store, if you attempt to conceal items on your person or otherwise, or even change the price tags on certain items, for criminal purposes you have attempted to steal or shoplift these items. Typically loss prevention will detain you once you have passed the point of the checkout/cash registers, but just before you leave the store with items. This is to show a lack of intent to pay for the items.

Yes. If you attemted theft of the store's merchandise but did not get past the cash register or out of the retail stroe, you can be prosecuted for either retail theft or attemted retail theft. Usually, a suveillance camera or a security guard will have observed a customer take merchendise off a shelf and conceal it in a shopping bag or on the person ( in a pocket or a backpack ). Yes, an arrest and prosecution is likely to follow.