People who were given up for adoption without their parents' permission want to bring authorities who allowed it to task

This year Randy Ryder will meet his mother for the first time.

When he was born in a hospital in Málaga, southern Spain, in 1971 the doctor who signed his birth certificate named his mother as Roswitha Huber, an Austrian woman who was unable to have children of her own.

It was only a dozen years ago, and after a childhood marred by his adoptive mother's psychiatric and drinking problems, that Ryder finally discovered he was not Huber's son.

Now he has become one of the first victims to prove what campaigners say was widespread abuse of their powers by Spanish doctors, nurses, registrars and church authorities, which saw them steal, sell or register babies to women who were not their natural mothers.

More than 1,000 Spanish families launched a campaign for justice and truth last year. Most are seeking lost children, siblings or birth parents.

"My mother found out about me from a BBC documentary about the campaign," Ryder, whose adoptive father was an American living in Spain, explained by telephone from his home in Austin, Texas. "She contacted me via Facebook, we did the DNA tests and now my 12-year search is over."

In Ryder's case his 65-year-old mother is an actress who once lived in Spain, but is now based in London. "We chat almost every day. We aim to meet in the next few months. It is a little bit strange because I have had 12 years to chew on this. We'll have to deal with it one step at a time."

Campaigners hold up Ryder's case as proof of how easily babies could be made to disappear or have their identities changed in a Spain run by dictator Francisco Franco – though other cases came after his death in 1975.

"The judge shelved my case the first time I brought it to the court," said Ryder. "But now I plan to appeal, because I want to prove legally that documents were falsified."

His is not the only case where identity switches have been proved. In another shocking encounter between mother and child, a woman who knew she was adopted discovered that – officially – she had been declared dead at birth.

When she contacted her birth mother, she was greeted like a returning ghost. "My mother reacted badly, insulting me," Maria, who used a false name, told El País newspaper.

"Who are you? What do you want from me? This is a bad joke, I gave birth to a child in that hospital and on that day, but it was a boy and it died," her mother replied.

But DNA tests have since proved the relationship. It is one of more than 1,400 cases that have been brought to Spanish courts.

Many, like Ryder's, have been shelved because of lack of evidence. But in a dozen other cases graves have been opened and bodies exhumed to see if children deemed dead and buried were not in their proper place. DNA tests have proved nothing was amiss in those cases, suggesting that some of the stories of abduction may turn out to be untrue.

While some campaigners blame Franco's regime, others point to a wider culture of abuse of power by authority figures.

Ryder has even confronted Dr Manuel Muñoz Nieto, the man who signed his birth certificate and still practises in Málaga. "He said he had no idea, that he just turned up for the birth," said Randy, who wants to see the doctor disciplined.

"Authority figures were never questioned at the time," he said. "I think most people adopted in Spain at that time probably didn't know – and still don't."

What infuriates campaigners, however, is the difficulty they are having with courts today. "The first time I contacted the Spanish consulate about this they told me I was crazy and suggested I had some hidden agenda," Ryder said. "And when you go to court the burden of proof is on the victim."

"They are not interested in clearing this up," said Antonio Barroso, an illegal adoptee who heads a campaign group.

So far courts have interviewed just two doctors allegedly involved in baby-trafficking and a nun will be quizzed soon.

"We have started our investigations, but we don't know where they will lead us," said the chief prosecutor in Málaga, Antonio Morales, who is looking at crimes potentially ranging from baby stealing to document fraud.

Ryder believes both regional governments, which control archives, and courts are still blocking investigations. That is why he will return to court soon. "My friends in Spain have told me it is hard to go against the state. I want to show that there is legitimacy in the things people are saying. If I can help them, then that is important to me."

His search has brought him close to other campaigners, including a Madrid woman who thought he might be her lost son, though DNA tests came up negative. "We are still close," said Ryder. "If my case can provide a bit of hope to people who are seeking, then it is worth its weight."