A double jeopardy inquiry can get a bit complex with multiple charges arising out of the same incident or chain of events. Typically the distinction is whether the two crimes share the same elements. If the more serious crime contains all the same elements but then just adds something more (like, say, malice) then the defendant cannot be convicted on both the lesser crime (usually called a lesser included offense) and the more serious offense. But if the lesser crime has elements to it that are not found in the more serious offense then a conviction on both may be had. Others have discussed that point already. Double jeopardy is not what is likely to present the problem here, though there is another potential issue involved here.
Consider the Carpenter case. In that Ohio Supreme Court case, the defendant stabbed someone on 9/6/1984 and was charged with felonious assault for the attack. The defendant and the state then agreed to a plea deal on 1/7/1985 where the defendant plead to attempted felonious assault. The victim then dies from the stabbing injuries on 3/28/1986. On 1/28/1988, shortly after the defendant's release from prison on the attempted assault charge, the state charged him with the murder of the victim. At issue here was not a double jeopardy claim. As the dissent in the case pointed out, there was no dispute that the subsequent prosecution would not be barred by double jeopardy:
It is well settled that a defendant may be tried for the murder of his victim even if he had been previously convicted of a lesser related offense prior to the victim's death. “The courts have long held that where a fact necessary to the commission of one offense occurs after the defendant has been convicted of another offense, multiple prosecutions are not barred by the Double Jeopardy Clause.” State v. Thomas (1980), 61 Ohio St.2d 254, 262, 15 O.O.3d 262, 267, 400 N.E.2d 897, 904.
State v. Carpenter, 1993-Ohio-226, 68 Ohio St. 3d 59, 62, 623 N.E.2d 66, 69. The Ohio Supreme Court had thus previously declined to consider the Appeals court ruling in this case that the prosecution was not barred by double jeopardy. But it did finally agree to hear the case on a different ground: whether the prosecution had to reserve the right to pursue additional charges when it made the plea agreement in order to now prosecute the murder case. And the court concluded that the prosecution did have to reserve that right, and since it hadn't, the prosecution was not allowed. The court stated:
In the present case, the state had actual knowledge of the alleged victim's condition at the time of the plea agreement and knew death was possible. Nevertheless, the state accepted a plea in which it agreed to reduce the charge of felonious assault to attempted felonious assault and recommend the imposition of a minimum sentence of two to ten years. By accepting a plea to a lesser included charge, the state obtained a definite prison term for the defendant and avoided the uncertainties of trial. In exchange, the appellant anticipated that by pleading guilty to attempted felonious assault, and giving up rights which may have resulted in his acquittal, he was terminating the incident and could not be called on to account further on any charges regarding this incident. We think this expectation was entirely reasonable and justified and that the prosecutor was aware of this expectation. Therefore, if the state wanted to reserve its right to bring further charges later, should the victim die, the state should have made such a reservation a part of the record.
Accordingly, we hold that the state cannot indict a defendant for murder after the court has accepted a negotiated guilty plea to a lesser offense and the victim later dies of injuries sustained in the crime, unless the state expressly reserves the right to file additional charges on the record at the time of the defendant's plea.
State v. Carpenter, 1993-Ohio-226, 68 Ohio St. 3d 59, 61–62, 623 N.E.2d 66, 68.
So while there is likely no double jeopardy bar in this case, if the guy took a plea deal and the state did not reserve the right to pursue additional charges if the victim later died then he cannot now be charged with her murder. The article is not clear on whether he took a plea deal or was convicted at trial, and that is a significant issue here.