Puerto Asis, Colombia - Esperanza Canencio sits in silence in the tiny living room of her house with a picture of her son behind her in the southwestern state of Putumayo.

For hours now, a van has been driving around the streets with a recording that blares into the houses located on Carrera 20, where more than 300 members of the Revolutionary Armed Forces of Colombia (FARC) make their way to a demobilisation zone to disarm and begin their transition to society.

"The war is over," the recording announces hopefully on this Thursday morning in late January, inviting residents to hang a white flag outside their homes. For Canencio, however, the conflict will truly end when her son, Edgar Bayron Murcia - a policeman kidnapped in 1999 by the rebels - returns to her: dead or alive.

"I say it with all my heart that I will forgive them the day they give me the remains, even if it's only the remains of my son. They should tell the truth, what did they do to him? Did they kill him? Well okay, what did they do with him?" says Canencio as she raises her hands in despair.

The conversation takes Canencio back to a prolonged and painful chapter of Colombia's recent past. Not that she has forgotten; it is closer to her than ever before, but while a negotiated peace serves to heal the country, Canencio's wound is still raw. Her son is still missing. In mere minutes, the roughness on her face softens as tears hang from the edge of her eyelids, ready to roll with the first memory.

It was in 2001 when the FARC's Eastern Bloc issued a statement saying Murcia had allegedly escaped from the camp where he was being held in captivity. From that moment, Canencio hasn't stopped asking herself the same question: where is her son?

For the families of the 45,630 missing people that the Colombian government officially recognises, the war is far from over.

Last November, the government and FARC guerrillas signed a landmark peace deal to end 52 years of armed conflict, in which both sides committed to recover and return the remains of tens of thousands of disappeared people. Rights advocates and victims' families demand more bodies be exhumed, identified, and returned to their families to signal the real beginning of the post-conflict era.

Now, as the mechanisms to establish truth, justice, and reparations begin to work - and the rebels start to reveal grave locations - forensic experts are preparing to deal with the overflow of bodies and skeletal remains.

Inside the lab

The bones of the light-yellow skull tinged with dark brown are joined with masking tape. On its left side, there is a bullet hole.

"It looks like a high-speed firearm, and it was shot from a close range … The great majority of our cases are by projectile," explains Carolina Forero Montealegre, forensic odontologist from the human identification team of the country's Crime Scene Investigators (CTI).

On the next table, an almost complete skeleton has two bones tied together with black rope, a clear sign of torture. They look like a tibia and a fibula.

"Here, all the cases enter by forced disappearance. This is an aggravation, the torture," adds Forero Montealegre.

Forced disappearances - a tactic used widely throughout Latin America by US-backed regimes - were practised in a massive and systematic manner to intimidate, eliminate government opponents without a trace, and punish those left behind with a life driven by grief, uncertainty, and stinging emptiness.

In Colombia, the agents of conflict - guerrillas, paramilitaries, drug cartels, and state security officials - forcibly disappeared 60,630 people between 1970 to 2015, according to a study from the country's National Center for Historical Memory released in 2016. Between 1996 and 2005, a person disappeared every two and a half hours.

On the six metal examination tables in the laboratory of the CTI in Bogota, everyone now looks the same. The bones range from a dirty beige to a pale yellow to a dark brown, and are fitted together as newly completed jigsaw puzzles. Most are missing pieces.

"The vast majority of our exhumations, the bodies are incomplete because they are never recovered 100 percent. But we find them," says Forero Montealegre. "Everything has an image of context, so there are some that we do not find, only the long bones or the skull or a dental structure. The anthropologists are very judicious and do their work to recover as much as possible."

The exhumation team is composed of the leading anthropologist, a photographer, surveyor, and a field assistant in charge of the systematic collection of physical evidence that can later be used in court. In total, according to prosecutor Carlos Villamil, the General Attorney's Office has 69 people working throughout the country on conflict-related cases.

The implementation of reparations for victims after serious human rights violations poses substantial challenges for the Colombian government, especially when many of the witnesses are buried in unmarked graves hidden in the hard-to-access jungle or in remote terrains. Determining the biological profile - sex, age, height, and other individual traits - of the exhumed human remains is the first step in uncovering various aspects about the victims' life history, and most crucial, about their deaths.

Establishing the possible cause of death and other facts is key in clarifying the truth, bringing closure to the affected families, and starting the long road to reconciliation.

'Open investigation'

Before entering the identification room there is a cellar where red plastic bags rest on metal shelves divided into sections: "evidence, graphic reconstruction, analysed, identified, remnants". Some remains are in the red bags, others in cardboard boxes. Each package, which stores what is left of a human being, is assigned to an interdisciplinary team: a doctor, an odontologist, and an anthropologist.

"They receive a folder that must have the required documentation for each of the bodies. The files contain a report of the examination, the archaeological record, and the request made by the prosecutor, since here we only work by orders of the prosecutor's office. It is not that we are just finding. There has to be an open investigation," says Forero Montealegre.

In 2005, in the framework of the negotiations with the paramilitary group United Self Defense Forces of Colombia, the state adopted transitional justice measures and mechanisms, such as the Justice and Peace Law, criticised by some as it offered reduced prison sentences for those responsible for serious human rights violations in exchange for full confessions. This, according to Villamil, director of the transitional justice unit, has allowed a large percentage of searches to begin when demobilised armed groups give their accounts of events.

"We obtain information on where the person may be, where they saw him. We collect information, what is called antemortem, that is everything that preceded the person: his family, his customs, dental record card, identity, photographs, a series of elements. Then we verify if we have a possible grave, a possible place of burial, whether clandestine or formal. It can be an unidentified person or with possible identity, and according to that, we proceed with the exhumation."

With coordinates in hand, the work team visits the site, which can be complex given the diverse topography of the country. Depending on the type of soil, tools such as Ground Penetrating Radars are used. These have gained popularity in recent years in their use to find bodies for their capacity to zoom deep and locate unmarked graves without altering the soil and associated evidence. If the terrain demands it, then manual tools, such as metal rods or soil probes, are used. As of July of this year, the prosecutor's office found 5,387 graves and exhumed 6,862 bodies, of which 3,482 were identified and returned to their families.

Colombia's largest forensic excavation to date is the infamous site La Escombrera (The Dump), a landfill located on the outskirts of Medellin and above the Comuna 13 - one of the city's poorest neighbourhoods - where heavy digging machinery was used in 2016 to explore a terrain of 3,700 square metres. After five months, no remains were found.

The disappearances go back to 2002, when the government launched a series of military campaigns such as "Operation Orion" against left-wing rebels, allowing right-wing paramilitary forces to take control of the area. The second phase of exhumation was to start in January 2016, but work has not resumed. Families and rights advocates believe the bodies of up to 300 people are buried under tonnes of rubble.

Never came back

For Martha Rosa Jimenez, who has lived in the Comuna for the past few years after being displaced from the countryside, visiting the landfill gives her the feeling of getting closer to her missing son. She had nine children, but the conflict took away from her three. Robin was killed on January 3, 1996, at age 16.

"He was shot five times in the stomach and I was told, at 8 o'clock in the morning, I was told to go to a certain place. There I was going to find Robin," she says, her voice still shaking with a tone of rage.

She lost her voice immediately after hearing the news. Three years would pass before it returned. Then in 2006, her son Juan was killed after a group of men suddenly burst into the house and took him away. Two years later, her 15-year-old son, Jony Alejandro, disappeared. He went out and never came back.

Once a body is recovered and depending on the conditions in which it was found, the laboratory that will examine it is determined. If the body is still in decomposition, it is sent to the National Institute of Forensic Medicine and Forensic Sciences (INMLCF). Skeletons and bone remains are sent to the laboratory of the National Police or the CTI.

Disposable caps, respirators, jumpsuits, and shoe covers wrap the bodies of the living entering the human identification laboratory where forensic anthropologists face the challenging task of identifying dozens of skeletal remains. Passing the portable X-ray desk, there is a washer and a dryer that looks like any household equipment, but are used to clean the pieces of clothing found during the exhumations. Next to them, there is a stainless steel washing table with sieves that are used when big pieces of dirt are brought in. The bones can't always be separated from other matter at the exhumation site because of different factors, such as time or level of risk. The sieves help filter small items, such as wrist and foot bones, to avoid them being lost.

"The cases arrive and they clean them," explains Forero Montealegre. "More than a washing process, it is a cleaning process. Depending on the type of sample, it's cleaned with a soft-bristled brush, or simply with a gauze, depending on the state of the bone."

The remains are placed on the metal table in anatomical positions so the team can work systematically, examining each bone, and provide a visual inventory. Each bone is marked with a number.

"Each of the bones, except for the tiny ones, are marked with a work order and the year. Look, here it says: work order 1109 of 2016," says Forero Montealegre, pointing at a pale white, medium-sized bone.

"Why do we mark them? In Colombia, we apply the chain of custody system so all the material obtained can be used in court. The same thing we collect, we take a photograph to show that it is the same."

At the head of each metal table, there is an information sheet. In the last line of the card, below the date and place of exhumation, there is a space for possible identity. Some have the infamous NN, which stands for "no name", but others have a possible name.

DNA extraction

The use of DNA in the identification of missing persons has advanced drastically since the Balkan War and the attack on the World Trade Center in 2001, the most expensive forensic investigation in the history of the United States.

"In genetics, what can happen?" says Forero Montealegre. "It can confirm that it's the same person; it can be inclusive or excluded. If it is excluded, we have a system called CODIS, where the information of the unidentified body is stored. If it is identified, then the process is done with the prosecutor so that the doctors prepare the death certificate, the death is recorded, and then it is returned to the relatives. But if it is not identified, the genetic profile is already in CODIS and we save it and leave it in the cellar outside of here, which is the transitional general warehouse where we store all the bodies until another process is done again because the investigation continues until it is conclusive."

The Combined Index System (CODIS) is a database, created by the FBI, of DNA profiles of convicted persons, missing persons, and forensic samples of crime scenes. In Colombia, the platform, acquired by INMLCF under Plan Colombia - a multibillion-dollar US aid package aimed to stop the flow of drugs by strengthening government forces - has about 30,000 genetic profiles and, according to Villamil, there are 8,000 samples waiting to be processed.

The genetic laboratory is sleek and airtight, full of machines that would intimidate any non-scientist. Here is where the DNA profile obtained from the skeletal remains and dental structures is crossed with reference samples, either blood or saliva from a close family member.

First photographs of the samples are taken to follow the chain of custody and then the method to be applied is selected, explains forensic geneticist Juan Ernesto Baquero. Either the bone fragment or dental structure is pulverised before the cell lysis occurs, a process that causes the breaking down of the cell's membrane to release the DNA.

"We use the centrifuges for DNA extraction," explains Baquero. "It's like having oil, and from oil, you take out gasoline … It does not mean that because we have standardised the process, we do not have difficulties. There are many difficulties."

The poor quality of skeletal remains is one of the main challenges. If it is a bone, for example, that was 10 years in a place with high humidity, there can be cases where all the genetic information is lost.

Although the tools are already there, understaffing is still an issue for the forensic unit.

"What we need is more people, more qualified personnel," Villamil says. "And we need to think about compensation. We have machines, but we need people. Before, we had no machines or people."

'Hand on their heart'

Canencio sighs deeply as she puts a glass of soda and cookies on the glass table, and her ponytail of black curls falls on her left shoulder. Her mouth looks tense as if the passage of time had stagnated in her round jaw. Her gaze drifts and wanders in the green landscape that glimpses beyond the semi-constructed houses of her neighbourhood. She comes back to the living room, and in an outburst of sudden exasperation, says: "With this [peace deal], I hope they put their hand on their heart and comply."

Working with the perpetrators is the biggest hope the families have to know where their loved ones are, and the use of forensic science to investigate human rights violations may be the only tool the Colombian government has to return the stolen stories of the past to the victims and their families, if that it's even possible.

It will definitely not be simple to find, exhume, and identify the tens of thousands of disappeared.

Canencio, with the picture of her son behind her, lowers her voice with a kind of resignation. "I see it difficult, but for God, there is nothing impossible."

This story was made possible thanks to a crowdfunding campaign by Press Start