Who is Clark Rockefeller?

Christian Karl Gerhartsreiter told a series of lies to his wife Sandra Boss.

Jurors in the kidnapping trial of the man who calls himself Clark Rockefeller - a German-born man who has spent decades making up lies about himself - have finished a second day of deliberations without reaching a verdict.

US authorities said Rockefeller, whose real name is Christian Karl Gerhartsreiter, used multiple aliases since moving to the United States in 1978.

The trial featured testimony from people who recounted elaborate tales Gerhartsreiter told about himself.

Besides pretending to be a member of the famous Rockefeller clan, he claimed to be a physicist, a ship's captain, an art collector and a debt negotiator for small countries.

He is accused of snatching his and ex-wife Sandra Boss's daughter during a supervised visit after losing custody to his ex-wife. Father and daughter Reigh were found in Baltimore six days later. The girl was unharmed.

Defence lawyers said Gerhartsreiter was delusional and legally insane when he fled with his seven-year-old daughter. But prosecutors call his insanity claim "preposterous" and say he planned the kidnapping for months after losing custody.

They said Gerhartsreiter spent months planning the kidnapping, buying a home in Baltimore under the false identity of a South American-based ship captain, converting an $US800,000 divorce settlement into untraceable gold coins and hiring two drivers to help him get away.

Who is `Rockefeller'?

Gerhartsreiter first moved to the United States from his home in Germany in 1978, and quickly began a series of lies, Assistant District Attorney David Deakin told the jury in Boston. In 1981, he convinced a Wisconsin woman to marry him so he could get a green card to remain in the country, and then quickly left her.

Over the next two decades, he concocted elaborate stories about himself, Deakin said.

When he first met Boss, he told her he restructured debt for poor countries and explained his lack of income by saying he didn't have the heart to charge struggling nations for his services. He also said he had attended a program for gifted children at Yale University when he was 14.

Boss was "dazzled" by his charisma and intelligence, Deakin said. The couple married in 1995, and in 2001, Reigh was born.

During the trial, Boss said she tried to leave her husband several times during their 12-year marriage, but he became angry, threatened her and told her she would lose custody of their daughter.

Boss said her ex-husband controlled their finances and would not give her access to their bank accounts. She said at times he did not give her enough food to eat and that she sometimes woke up hungry.

"The defendant on one occasion, when I told him that I was strongly considering getting divorced, started screaming at me in front of Reigh and told me that if I did, he would manage to get full custody of her," Boss said.

Boss said she was smart in the business world, but did not make a "very good choice of a husband".

"It's pretty obvious that I had a blind spot," she said. Boss said it's possible for someone to be "really brilliant" in one area of life and "really stupid in another".

Boss said she knew her husband told some lies to other people to make himself seem more important, but she only discovered the extent of his deception when she hired a private investigator during the divorce.

It was during that time that Boss asked for full custody of her daughter, saying she questioned her husband's "very identity", Deakin said.

The divorce agreement awarded Boss full custody. Gerhartsreiter accepted a settlement of $US800,000 from Boss and agreed that he would have three supervised visits with his daughter each year.

But on July 27, 2008, Gerhartsreiter allegedly snatched his daughter, shoving a social worker to the ground and pushing the girl into a waiting car so quickly that she hit her head on the door frame and began to cry, Deakin said.

"In his mind, the rules don't apply to him," Deakin said, a theme he repeated throughout his remarks to the jury.

But Gerhartsreiter's defence lawyers said his actions were linked to his mental illness. Defence attorney Jeffrey Denner described the illness as a delusional disorder and a narcissistic personality disorder.

He said Gerhartsreiter was so mentally ill that he came to believe his own stories, even "the notion that he was a Rockefeller".

His daughter, he said, provided the "only reality" in his life, and he was distraught when he lost custody of her.

"Without her, he was nothing," Denner said.

A couple's disappearance

After his arrest in his daughter's kidnapping, authorities in California identified Gerhartsreiter as a "person of interest" in the disappearance and presumed slayings of Jonathan and Linda Sohus, a newlywed couple from San Marino, California.

Gerhartsreiter, who was then using the name Christopher Chichester, was staying in a guest house on the couple's property when they disappeared. He has not been charged in that case and has denied any role in the couple's disappearance.

Jury deliberations resume on Wednesday local time.