Here's what we know about the trial of alleged Alexandria, Va., serial killer Charles Severance who is being charged in the murder of three Alexandria residents over the course of a decade. (Ashleigh Joplin/The Washington Post)

When prosecutors try this week to convince 12 jurors that the peculiar white-bearded man sitting in front of them is a killer who terrorized Alexandria, they’ll have to do so without a murder weapon, without DNA or fingerprints, and without any evidence that he had a relationship with, or had even met, the three victims.

The case against Charles Severance, who turned 55 last month in the Fairfax County jail, is a circumstantial one, predicated largely on Severance’s voluminous writings and ballistics evidence that isn’t as conclusive as prosecutors might like.

There might be an eyewitness to one killing — a woman who was shot during one of the three incidents in which Severance is accused. Another person thinks she saw Severance near that shooting scene. And there will be evidence that prosecutors argue puts Severance at a store with another victim soon before she was shot.

But the case, experts say, will require prosecutors to put the pieces of the puzzle together and craft a narrative about Severance that convinces jurors he is guilty.

Charles Severance, center, talks to defense attorney Joe King as he appears in Fairfax County Circuit Court on Oct. 1. (Matt McClain/The Washington Post)

“They have a lot of circumstantial evidence,” said John Kenneth Zwerling, a veteran criminal defense attorney in Alexandria who is not involved in the case. “They don’t have very much direct evidence, so I think what they’re going to try to do is poison the jury against the defendant.”

Severance is charged with murder in the February 2014 slaying of music teacher Ruthanne Lodato, the November 2013 fatal shooting of regional transportation planner Ronald Kirby and the December 2003 killing of real estate agent Nancy Dunning. His trial is scheduled to begin with jury selection Monday, and those involved have said it could last up to six weeks.

Months ago, the case was moved from Alexandria to Fairfax County over concerns about seating a fair jury, and it will be overseen by Judge Randy I. Bellows, who replaced Judge Jane Marum Roush after her appointment to Virginia’s Supreme Court. More than 100 witnesses could testify, ranging from a woman who claimed to have seen Severance run a stop sign near the scene of one of the killings to a man who tested and sold a board game that Severance invented.

The trial will be an emotional, perhaps unpredictable affair. In the past, Severance has sparred with the judge and interrupted his own attorney. He once requested that his attorneys purchase him a specific type of kilt to wear to court.

Anne Haynes, Kirby’s widow, said in a brief phone interview that she expects to be called as a witness, and she is anticipating a heart-rending experience.

“It’s very, very painful for me to deal with Ron’s death,” she said.

Haynes said she wants to learn some new details during the trial — including a thorough accounting of how Severance was able to obtain the weapons prosecutors say he used — although she is not looking for a particular outcome.

“I’m not anybody who wants revenge, that’s for sure,” she said.

John Kelly, a Lodato family spokesman, said in a statement: “We’ll never understand why this happened and nothing will bring Ruthanne back. In the end all we can hope for is some measure of peace in our heart.” Dunning’s daughter declined to comment, as did prosecutors and defense attorneys.

Prosecutors have alleged that Severance was motivated to kill by a child-custody dispute that went against him and a general hatred for those he considered Alexandria’s elites. Their most convincing piece of evidence might be Severance’s writings, seized from his car and through various electronic means.

In one document, Severance wrote, “Knock. Talk. Enter. Kill. Exit. Murder” — an apparently perverted version of a biblical parable that prosecutors have argued seems to describe the crimes to a T. All of the victims were shot in brazen, daylight attacks at their homes, and prosecutors have said Severance might have simply gone to their well-to-do neighborhoods and picked them at random.

Defense attorneys will counter that Severance’s writings were nonspecific and rambling and that none mentioned any of the victims by name. They have lined up witnesses, including a mental health expert and one of Severance’s friends, to help explain the documents in ways that don’t make them evidence of murder.

The mental health expert concluded that Severance suffers from a personality disorder with mixed paranoid and schizotypal features. The friend scheduled to testify is a man who once sold a game Severance developed.

The attorneys have made clear in pretrial hearings that they hope to argue that Severance’s writings did not espouse real violence, but only references to an unconventional fantasy game or the random musings of a man with a troubled mind. Experts said the arguments could be convincing.

“It may be that the writings are just so bizarre that there’s no way to interpret them at all,” said Peter Greenspun, another attorney who is not involved in the case.

Defense attorneys also intend to argue that in at least one case another man was responsible. The judge ruled last month that in Dunning’s killing, they can point the finger at the late James Dunning — her husband and the former Alexandria sheriff.

That argument, experts say, might also be persuasive. Defense attorneys asserted previously that Dunning cheated on his wife and gave inconsistent statements to police about it, resisted her requests that they seek marital counseling and gained significant wealth after she died. Also, during a 911 call from the scene of the slaying, he said that his wife had been “murdered” — before the cause of death was clear.

Although prosecutors have asserted that Dunning is not responsible, and sought to block defense attorneys from even suggesting so, Alexandria detectives seemed to have him in their sights for years, defense attorneys have said.

Greenspun said that if defense attorneys convince jurors that Severance did not commit one of the killings, “that could bring about the failure as to all three.”

To be sure, Dunning, who retired to Hilton Head, S.C., several years after his wife’s death and died in 2012, is not a cure-all for the defense. Prosecutors intend to show surveillance video that they contend captured Severance at the Target store where Nancy Dunning was last seen alive, although defense attorneys dispute that the person on the tape is their client.

In the Lodato killing, prosecutors have a potential eyewitness: a woman who worked as an aide in the home and was shot and wounded by the attacker. She helped generate a police sketch that looks remarkably like Severance, and prosecutors have said that she might be able to identify him in court.

To link all three cases, prosecutors have ballistics evidence, although jurors will have to weigh what it means to them, since investigators have not recovered a murder weapon.

Prosecutors have said that a different gun was used in each killing but that all were the same type, and there is evidence that Severance had three guns of such a variety around the time of all three killings. Gun experts, prosecutors have said, will testify that the killings were the only ones in which they had seen the type of ammunition used, and Severance wrote of his fascination with that ammunition.

It is by connecting dots like those, experts said, that prosecutors will make their case. Although the evidence might not be direct, that does not make it weak.

“People will say, clients will say, ‘It’s only circumstantial evidence,’ ” Greenspun said, “but if all the pieces fit, then it can be very, very compelling.”