It altered the substantive criminal law.

It visited an offence with a penalty of which the offender, at the time when he offended, had no notice.
It may be thought a strange proposition that the bill against Duncombe was a worse bill than the bill against Fenwick, because the bill against Fenwick struck at life, and the bill against Duncombe struck only at property.

Yet this apparent paradox is a sober truth.

Life is indeed more precious than property.

But the power of arbitrarily taking away the lives of men is infinitely less likely to be abused than the power of arbitrarily taking away their property.