You do know what the scientific method is, yes?
I don't see a way you can abuse the scientific method. Rather, you could deviate from acceptable scientific practices by not following the scientific method. Some examples: tampering with results, not correctly documenting everything, throwing out data that contradicts the result that you want. This can happen in any field, and I don't know of any examples specific to genetic engineering.
I think what you are really looking for is examples of unethical research. For instance, if you were to engineer genes from another species into a human embryo, this would probably be unethical.
