He's been charged with embezzling SNP funds, while he was party leader. It's not yet clear how much Nicola Sturgeon knew and whether she'll be charged too.
The big question is, how does this affect the SNP's vote.
For those who donated money to the SNP, there may be a bitter taste in their mouths, though some may just shrug and chalk it down to experience.
For those who want the UK to remain intact, but voted SNP in the Holyrood elections because they "stood up for Scotland", there'll be disappointment. Especially as the SNP had promised cleaner politics. Some will drift back to Labour, the LibDems and Tories.
But die-hard Scottish Independence supporters will not budge. Just as lots of Brexit voters disliked Nigel Farage and Michael Gove intensely, but voted to leave the EU as a point of principle, lots of Independence voters want to return Scotland to it's pre-1707 state as a point of principle.
Shennanigans in the SNP don't count because they regard Sturgeon, Murrell and co as disposable. Besides, who else will they vote for? The only other Indy party, Alba, has no presence.
Finally, no tax money is involved. Experience shows that voters shrug off sleaze scandals and sex scandals. They only get interested when it affects them. So if tax money is involved or a policy is enacted that affects them.
So First Minister Humza Yousuf's incompetance will have a bigger bearing on the election than Peter Murrell being charged and tried.