Yes, absolutely, and this is why fraud detection is often as much art as science.
In the example above, you have someone coming in making a large purchase, which is probably odd if you've never seen this person before (eg: you would have expected them to come in and "kick the tires" and talk to employees a few times before making the actual purchase, even if they did a lot of online research). Plus the non-working card, and being late in the day. Of course, it's also possible that the whole transaction could be legit. If you suspect fraud though you can often do or say things to gauge the persons response. Tell them that for such an expensive purchase you'd really like to tune the bike up and make sure it's perfect, can they come back and pick it up first thing in the morning? Stuff like that, if the person accepts that, or seems to genuinely consider it, it's probably not a fraud sale. If their immediate reaction is "no way", or they get defensive, it could be a red flag.
In the example above, you have someone coming in making a large purchase, which is probably odd if you've never seen this person before (eg: you would have expected them to come in and "kick the tires" and talk to employees a few times before making the actual purchase, even if they did a lot of online research). Plus the non-working card, and being late in the day. Of course, it's also possible that the whole transaction could be legit. If you suspect fraud though you can often do or say things to gauge the persons response. Tell them that for such an expensive purchase you'd really like to tune the bike up and make sure it's perfect, can they come back and pick it up first thing in the morning? Stuff like that, if the person accepts that, or seems to genuinely consider it, it's probably not a fraud sale. If their immediate reaction is "no way", or they get defensive, it could be a red flag.