It is difficult to say what the after-shock of this ruling will be.  What is clear is that there will be many people serving hefty sentences, having been convicted on a joint enterprise basis, wondering if they can appeal conviction.  

It is important to note what the judge has essentially said is that “foresight” is an insufficient test to convict anyone of murder on a joint enterprise basis. What the Judge actually said was:

“The correct position is that … foresight of what the principal might do is evidence from which the jury may infer that he intended to assist or encourage to do so,” Lord Neuberger, the president of the supreme court said, “but it is for the jury to decide on the whole evidence of whether he had the necessary intent.”

The ruling does not entirely change the position regarding joint enterprise. It does not mean that all convictions are unsafe, but cases where "foresight" was a test that was applied will no doubt be looked into.  This may apply to only a few cases. The more common rule applied is that a person who intentionally encourages or assists the commission of a crime is as guilty as the person who commits it. This it seems is the correct test to apply when determining whether a person is guilty of committing a crime on a joint enterprise basis.  

It maybe that in the majority of cases the correct  test was applied.  It is generally left to a jury to decide if the person has intentionally encouraged or assisted in the crime and foresight can be evidence of this.

Today’s ruling applies to a murder conviction, but it maybe that others will look to apply this ruling to test convictions in cases where people were convicted of other offences on a joint enterprise basis, such as fraud.  Any person looking to appeal would need to demonstrate that they suffered substantial injustice.  

It is likely that at the very least, a flood gate of inquiries will follow with convicted clients queuing up to contact their solicitors to see if they have any grounds to appeal their conviction.