The Pan Am jet came down in Lockerbie in 1988, killing 270 people

The civil suits seeking damages from Libya were delayed several times as courts tried to determine if a private suit could be lodged against a foreign government. Mr Zaid's case has twice gone to the US Supreme Court, to determine whether Libya could be subject to such a suit.

In 1997, the Supreme Court let stand a lower court ruling that Libya could not be the subject of a civil lawsuit, saying that a foreign government has sovereign immunity shielding it from such suits. �

However, due to pressure from the families of Lockerbie victims, the United States amended the Foreign Sovereign Immunities Act in 1996, opening the way for civil suits against foreign governments in certain cases - including acts of terrorism. �

Following the passage of the Anti-Terrorism and Effective Death Penalty Act in 1996, many families of Lockerbie victims renewed their suits. �

In 1999, the US Supreme Court heard another case involving a civil suit against Libya in connection with the Lockerbie bombing, and based on the change in the law, the court ruled that families of the Lockerbie victims could proceed with their case seeking damages from Libya. �

Sending a message

In asking for $20bn in damages, Mr Zaid said the families want the Libyan Government to be held responsible for what they allege is the nation's involvement in the bombing.

Libya's leader Colonel Gaddafi with Al Amin Khalifa Fhimah

"We also want to send a message to state sponsors of terrorism that if you murder an American, you will be called to pay both criminally and civilly," he said - adding that a large amount is necessary to ensure the message is felt. �

If successful, the suits would represent some of the largest awards ever resulting from civil cases. �

In July 1999, General Motors was ordered to pay $4.9bn as a result of a suit brought by six burn victims who were disfigured in crashes involving GM cars.

It was the largest award in a product liability suit up to that time. By comparison, in the civil lawsuit against OJ Simpson regarding the deaths of his ex-wife Nicole Brown Simpson and Ronald Goldman, the jury awarded $8.5m to the Goldman family.

But the award against GM was soon eclipsed when a Florida jury ordered tobacco companies to pay $145bn to sick smokers in the state. The suit is likely to be tied up in appeals for years.

Complicated case

Relatives will not give up their fight for justice

However, unlike these product liability suits, the families of Lockerbie victims face unique challenges in bringing their cases, said Peter Buscemi, a lawyer with the Washington DC law firm Morgan, Lewis & Bockius. �

Mr Buscemi is a former assistant to the Solicitor General in the US Department of Justice, and he has been involved with a variety of civil litigation. �

A civil suit against a foreign government entails a whole series of issues in addition to those faced in typical civil suits, he said. �

In a typical civil case, plaintiffs can ask the defendants to turn over documents, provide witnesses and respond to written questions during what is called the discovery process.

But in the cases brought by the Lockerbie families, said Mr Buscemi, there is a question of whether Libya will be willing to subject itself to demands from courts in the US. �

And even if a judgement is obtained, there is the question of obtaining compensation. �

It is pretty straightforward when suing General Motors or Joe Smith, said Mr Buscemi, but not quite so easy when dealing with a foreign government.