Most likely wet-lay, as it's difficult to keep the weave pattern looking straight when applying resin by hand. There's no reason why the pattern shouldn't be completely straight when infusing.  

As Hanaldo said, assuming that infused parts haven't been made with an in-mould coating, the only obvious way of telling the difference between those and pre-preg parts would be to look at the 'B' side for evidence of the different release film/fabrics that are commonly used

The OP's parts certainly seem to be pre-preg ones, judging by the appearance of the 'B' side