I think the same would apply to biomarkers: they might raise awareness but definitely wouldn't bring certainty that violence WILL occur. It's pretty dangerous to make assumptions based on the fact that you "might" become violent.
Definitely, but they know that already. It's genomics 101: a marker is not a 100% sign that a phenotype will develop. They undoubtedly describe their research as being primarily useful in identifying factors that make violence more likely. Their goal wouldn't be "Lock up everyone who has X Y and Z markers." Their goal would be "Identify markers that, in conjunction with other things like abuse as a child, drug problems, etc, could increase the chances that someone is going to become violent, understand how those genes work, and maybe develop drugs to be given in some circumstances."
Put another way, if these researchers were so uninformed as to think that there is a DNA sequence which will tell them with 100% certainty that someone is going to commit violence, then they're not actually scientists and we don't need to worry about them accomplishing anything.
IF they identify markers for violence, THEN we will need to concern ourselves with making sure society doesn't take that as a certainty. Society has decided that sex offenders usually having a high rate of recidivism means that every individual sex offender is going to commit another sex offense, so we should lock them up forever. But that's for people who have already committed a crime. Being sexually assaulted as a child increases the chances of one becoming a child molester, yet we don't victims as ticking time bombs. People with these markers won't have committed a crime already, so perhaps society IS mature enough to handle it.