You can... use the scientific method to figure out ethical questions? Are you sure? Let's see...

Observation: murder exists

Hypothesis: murder is wrong

This already violates the scientific method, because the hypothesis doesn't explain the observation in the first place. Murder being wrong doesn't explain why it exists. Let's try it another way.

Observation: people think murder is wrong

Hypothesis: murder is wrong

Now we're getting somewhere! Except, well, we already have scientific explanations for why people think murder is wrong (namely in the fields of evolutionary biology and sociology). This extra hypothesis seems to be a violation of Occam's razor. But let's say those other explanations are insufficient. What's the next step? Predictions, of course! Now, what predictions does the hypothesis "murder is wrong" make? Well... it doesn't seem to make any predictions. At most, one could argue that, if the hypothesis "murder is wrong" is going to be scientifically meaningful, it must make the prediction "we will be able to build a measurement device that measures the "wrongness" of murder". But of course, no one knows how to build that device. If not unscientific in principle, this hypothesis at the very least seems to be outside what current science can discover.

Do you disagree? Do you think the hypothesis "murder is wrong" makes any other testable (in principle or in practice) predictions?